Your FREE ASE B4 Flashcards 2026 – 200+ Cards

Structural damage that is a change in LENGTH — the structure is shortened or folded, usually from a front or rear impact.

Structural damage that is a change in HEIGHT — part of the structure drops below or rises above its datum dimension, often at the cowl or rails.

Structural damage that is a change in WIDTH — the structure shifts off the centerline to one side, leaving uneven side-to-side measurements.

Damage in which one corner of the structure is higher and the diagonally opposite corner lower — the structure is no longer flat. Found with diagonal/datum measurements.

Damage in which one side rail is driven rearward relative to the other, making the structure a parallelogram. Found with X (cross) diagonal measurements.

A sharp, abrupt crease or fold (radius about equal to or smaller than the metal's thickness). A kink is repaired by replacing or sectioning, NOT straightening.

A smooth, gradual deformation over a broad area (radius larger than the metal's thickness). A bend can usually be straightened and reused.

A bend can be straightened; a kink must be replaced or sectioned. The OEM procedure always overrides the general rule.

Securing the vehicle to the bench or rack at multiple points so a pull moves only the damaged area, not the whole vehicle.

So the correcting force acts on the damage and not the whole car; a single anchor lets the vehicle move instead of the metal.

Apply corrective force opposite the way the damage went in, relieving the last damage first, to unfold the structure the way it folded.

Pulling slightly past the target so that when the force is released and the metal springs back, it lands on the correct dimension.

Working or warming the metal within allowed limits during a pull to release locked-in stress so it returns toward its original shape and stays there.

A measuring bar with adjustable pointers used to check point-to-point dimensions on a frame or structure against the OEM spec.

A hanging gauge with a centerline pin that shows whether structural points line up with the vehicle's centerline by sighting the gauges.

A separate ladder or perimeter frame, common on trucks and some SUVs, to which the body is bolted. Measured and repaired differently from a unibody.

A full frame whose side rails run around the outer perimeter of the passenger area, with crossmembers tying the rails together.

A full frame with two straight side rails joined by crossmembers like the rungs of a ladder; common on pickups.

A structural member that ties the two side rails of a frame together, adding strength and maintaining width.

Comparing crossing diagonals of a structure; equal diagonals mean the structure is square, unequal diagonals reveal diamond or sidesway.

The OEM's published length, width, and height spec for every structural control point, used as the target for measurement.

Underbody = floor pan, rails, and crossmembers; upperbody = pillars, roof rails, and aprons. B4 covers diagnosing and repairing both.

A bench or rack with anchoring and pulling towers that apply controlled force to restore structural dimensions while the vehicle is measured.

The movable post on a frame machine that anchors a chain to apply directional corrective force during a pull.

Comparing matching points on the left and right sides; equal symmetrical readings confirm the structure is straight.

Recording before/after measurements, the procedures followed, and that OEM specs and corrosion protection were restored, to verify the repair.

Re-measuring all control points after the pull to confirm length, width, and height are back within tolerance before refinishing.

The tendency of pulled metal to relax back toward its damaged position when force is released; the reason for over-pulling.

Secondary damage caused as collision energy travels through the structure beyond the point of impact.

Before to plan the pull, during to monitor progress and avoid over-pulling, after to verify the structure is back to spec.

Symmetrical = left and right sides mirror each other; asymmetrical = sides differ, so you must use the OEM chart rather than side-to-side comparison.

The route impact force travels through the structure; understanding it tells you where to look for hidden secondary damage.

Looking for buckles, cracks, tears, wrinkled metal, and disturbed corrosion protection as first clues to structural damage.

A sign the metal has been stretched past its limit; that area generally must be replaced or sectioned rather than pulled further.

Heat may be used within limits on mild steel to relieve stress, but must be strictly limited or avoided on high-strength steel.

A localized collapse or fold in a structural member caused by compressive collision force.

Body alignment is panel gaps and fit; structural alignment is the underbody/upperbody dimensions that determine those gaps.

Reapplying weld-through primer, anti-corrosion coatings, and seam sealer wherever the original coating was disturbed during repair.

Relieve major structural pulls and crush before fine-tuning; correct length, width, and height roughly, then re-measure and refine.

The maker engineered the structure for crash energy management; only the OEM-proven method restores that designed performance.

The systematic inspection and measurement that identifies all primary and secondary damage and determines the repair plan.

Mash = length, Sag = height, Sidesway = width. Naming the condition tells you which dimension to restore.

Structural damage not visible from the outside, found only by measuring; collision force can distort points far from the impact.

Designated pinch-weld or sub-frame locations the OEM specifies for clamping the vehicle to the bench.

Straighten a bend back to spec; section or replace a kinked or torn area at an OEM-approved location.

Recording measurements, materials, procedures, and corrosion protection so the repair can be verified to OEM spec.

Re-measuring, inspecting welds and corrosion protection, and confirming OEM procedures before releasing the vehicle.

Construction in which the body panels and structure form a single welded unit that carries the loads, instead of a separate body on a full frame.

Checking every structural control point in length, width, and height against the maker's dimension chart.

An imaginary, perfectly level horizontal plane (usually below the vehicle) from which all HEIGHT dimensions are measured.

An imaginary line dividing the vehicle into equal left and right halves; the reference for all WIDTH measurements, checked first.

A fixed reference (often at the front) from which LENGTH dimensions are measured along the vehicle.

It establishes a known symmetrical reference; if the center is off, all width comparisons are meaningless.

A specific structural location (hole, hardpoint, or fixture position) with a published length/width/height dimension on the OEM chart.

Tram and self-centering gauges that compare structural points to the dimension chart by physical measurement and sighting.

A system using sensors or a probe and software to compare the damaged vehicle to a stored factory database in real time.

Uses laser targets and a reference to compare structural points to spec, giving precise three-dimensional readings during the pull.

Vehicle-specific fixtures that bolt to OEM control points; if a fixture won't fit, that point is out of spec.

Adjustable measuring equipment set to OEM data, used across many vehicles instead of vehicle-specific fixtures.

Steel stronger and thinner than mild steel. It tolerates little heat — heating beyond the OEM limit ruins its strength — so it is often repaired cold or replaced.

Very strong steel (boron, martensitic grades) used in the safety cage (B-pillars, rockers). Usually replaced at factory seams, not heated or straightened.

An ultra-high-strength steel used in critical safety structures; typically cold-cut and replaced, never heated or pulled.

High-Strength Low-Alloy steel — a common high-strength grade that is stronger than mild steel but more heat-sensitive.

Heat above the maker's temperature limit destroys the engineered strength of high-strength steel, so heat is limited or avoided.

Pulling high-strength steel without applying heat, within OEM limits, to avoid weakening it.

Replacing only part of a structural component by cutting and joining at a location other than a factory seam — only where and how the OEM permits.

Chosen only where the maker allows, using the specified cut and joint; never at random, because the joint must restore original strength.

A common sectioning joint: the two ends butt together over an inserted backing/sleeve that reinforces the weld.

Removing and replacing a structural part at its factory seams when sectioning is not permitted or practical.

An original joint where the maker welded panels together; the default place to separate and replace a structural part.

Structure designed to fold and absorb collision energy; it must be restored to OEM spec so it crushes correctly next time.

The ultra-high-strength structure (pillars, rockers, roof rails) protecting occupants; usually replaced, not straightened.

A main fore-aft structural member that carries load and manages crash energy; measured in three dimensions during repair.

Upperbody structure supporting the suspension and engine cradle; measured to keep wheel alignment and panel fit correct.

A bolt-on or welded structure carrying the engine and suspension; its mounting points are key measured control points.

The structure at the base of the windshield joining the firewall, fenders, and inner panels; a common sag/datum reference area.

A flanged, spot-welded structural seam (e.g., rocker) used for anchoring and as a control point.

Recording all control points before pulling so the technician can see every misaligned dimension and plan the corrective force.

Re-measuring all points after the pull to confirm length, width, and height are within tolerance.

The acceptable amount a structural dimension may vary from the OEM spec (often a few millimeters) and still be considered correct.

A structure built of aluminum, which requires an isolated work area, dedicated tools, and often rivet-bonding instead of welding.

Corrosion that occurs when steel and aluminum particles contact; the reason aluminum work is kept in a separate isolated area.

Joining structure with structural adhesive plus rivets; common on aluminum and on some steel joints per OEM.

A rivet that pierces and joins panels (often aluminum) without a pre-drilled hole, set with a dedicated tool per OEM.

To prevent steel dust from contaminating aluminum and causing galvanic corrosion, and to keep dedicated tools uncontaminated.

Using engineered structural adhesive, often with welds or rivets, where the OEM specifies it to join panels.

Because the body is one unit, impact force travels through it, so damage and the order of repair often involve the whole structure.

Mounting fixtures or gauges incorrectly gives false readings; verifying setup against undamaged points prevents chasing phantom damage.

Thin high-strength panels spring back when force is released, so a slight over-pull lands the dimension on spec.

A reinforced location (hole or bracket) used as a measuring control point or fixture mount.

On asymmetrical vehicles you must use the OEM three-dimensional chart, since the two sides are not mirror images.

Reapplying weld-through primer between mating flanges, anti-corrosion coatings, and seam sealer after structural repair.

Thin, hardened steel loses strength quickly with heat, so straightening relies on measurement and cold pulling, not heat.

Before cutting, heating, or pulling, identify the metal (OEM data) so you use a procedure that won't destroy its strength.

The stored OEM dimensions in an electronic/computerized system used to compare the damaged vehicle in real time.

Each control point on the chart has all three dimensions; a point can be correct in two and out in the third.

Where the OEM prohibits sectioning or the part is ultra-high-strength; then replace at factory seams.

Some structural parts are bolt-on (cradle, bumper reinforcement) and others welded; replacement method follows the original.

Critical for wheel alignment; small structural shifts here change alignment angles, so they are measured carefully.

Inspecting and measuring to build a complete repair plan before any cutting or pulling begins.

Three-dimensional measurement, not pulling force, is what makes a structural repair correct and verifiable.

The maker engineered the structure; published procedures reflect testing the general rule may not, so they take priority.

Replacing seam sealer, sound deadeners, and foam fillers disturbed in repair so noise, vibration, and water control return to factory.

A correct B4 repair is measured, OEM-procedure-driven, corrosion-protected, verified by re-measurement, and documented.

Glass bonded permanently to the body — the windshield and back glass — as opposed to movable door glass.

The structural adhesive that bonds stationary glass to the body; it contributes to structural integrity and air-bag performance.

A bonded windshield adds to roof-crush resistance and helps proper passenger air-bag deployment, so the bond is structural.

The flanged body edge around a glass opening to which the glass is bonded; must be cleaned, trimmed, and primed.

Trim the old urethane to a thin, even layer rather than to bare metal, giving the new bead a compatible surface to bond to.

Fresh urethane bonds best to the original cured urethane, so a thin layer is left rather than cutting to bare metal.

Any bare metal exposed on the pinchweld must be primed to prevent corrosion and ensure the urethane adheres.

The black ceramic band on the glass edge; it and the glass are primed so the urethane bonds and is protected from UV.

The time the urethane needs to cure to a strength that will hold the glass in a crash before the vehicle can be returned.

Releasing the vehicle early risks the glass not holding in a crash, compromising occupant protection and air-bag function.

The continuous, correctly shaped (often V-shaped) bead of urethane applied to bond the glass with the right gap and strength.

Aligning and seating the glass on the bead with even pressure and correct positioning before the urethane skins over.

Tools used to cut the old urethane and free a bonded glass for removal without damaging the pinchweld.

Glass that comes as an assembly (with moldings/encapsulation) and is bonded as a unit to the body opening.

Oil, dust, or moisture on the pinchweld or frit weakens the urethane bond, so surfaces are cleaned per the adhesive maker.

Older glass used a rubber gasket; modern stationary glass is urethane-bonded and structural, requiring proper prep.

Only the specified high-modulus structural urethane meets the strength and drive-away requirements for the structural bond.

The passenger air bag can deploy against the windshield, so a poor bond can let the glass push out and reduce protection.

After install, checking for water leaks and wind noise confirms a continuous, properly seated urethane bead.

The trim around stationary glass; reinstalled correctly so the bond and appearance are maintained.

Glass with a molded-in trim/molding edge; handled and bonded so the encapsulation and seal stay intact.

Bent or corroded pinchweld is repaired and primed before bonding, since the bond is only as good as the surface.

Wearing cut protection and supporting the glass so it does not fall while cutting it free from the urethane.

Urethane cure speed and safe drive-away time depend on temperature and humidity per the adhesive maker's chart.

One-part cures with moisture in air; two-part cures chemically and can reach drive-away strength faster.

Loose or contaminated old urethane breaks the chain of adhesion, so it is trimmed to a sound, clean thin layer.

Gas Metal Arc Welding — feeds a continuous wire electrode with shielding gas; the most common structural steel welding method.

Gas (often a CO2/argon mix for steel) that shields the molten weld from air to prevent porosity and weak welds.

Squeeze-Type Resistance Spot Welding — clamps steel between copper electrodes and passes current to make a spot weld, duplicating factory welds with low heat.

It recreates the original factory joining method and adds little heat, preserving the strength of high-strength steels.

A lower-temperature joining method using a silicon-bronze filler, specified by some makers for high-strength steel to avoid heat damage.

Its lower heat input reduces the heat-affected zone and protects the engineered strength of high-strength steel.

A weld made through a hole drilled or punched in the top panel to join it to the panel beneath, simulating a spot weld.

A weld joining two pieces edge-to-edge in the same plane; used in sectioning, often with backing for strength.

A weld joining two overlapping panels along the overlap edge.

A practice weld on the same metal and thickness as the repair to verify the welder is set up to make a full-strength weld.

Destructive testing of a coupon confirms penetration and strength before welding the actual structure.

How deeply the weld fuses into the base metal; too little is weak, too much can burn through thin high-strength steel.

Gas pockets in a weld (from contamination or poor shielding) that weaken it; a reason to clean metal and check shielding gas.

The area around a weld whose properties change from welding heat; minimized on high-strength steel by limiting heat.

A conductive zinc primer applied between mating flanges so the joint can be welded while still protected from corrosion.

Reciprocating saws, plasma cutters, and spot-weld cutters used to remove damaged structure with controlled heat and minimal collateral damage.

A tool that drills out factory spot welds to separate panels at a seam without distorting the surrounding metal.

Plasma cuts quickly but adds heat, so it is used carefully (often only for removal) on heat-sensitive high-strength steel.

Removing paint, rust, coatings, and oil so the weld fuses cleanly and is free of porosity.

Warping from welding heat; controlled with stitch/skip welding, clamping, and limiting heat input.

Welding in spaced intervals and letting the metal cool to reduce heat buildup and distortion on thin panels.

Aluminum is welded with a spool gun or push-pull feeder and argon shielding, in an isolated area with dedicated tools.

GMAW typically uses DC electrode positive (reverse polarity) for good penetration on steel.

Metal placed behind a butt joint (especially in sectioning) to reinforce the weld and control penetration.

Restoring weld-through primer, anti-corrosion coatings, and seam sealer on all welded structural joints.

Welding helmet with the correct shade, gloves, and fire-resistant clothing, plus protecting glass, trim, and airbags from heat.

Disconnecting the battery and protecting modules so welding current does not damage vehicle electronics.

The copper tips on a resistance spot welder that conduct current and squeeze the panels; kept clean and dressed for good welds.

The wrong weld or too much heat on high-strength steel destroys the strength the structure relies on for crash performance.

GMAW settings that control heat and deposition; set per metal thickness and confirmed with a test weld.

Melting a hole through thin metal from too much heat; avoided with correct settings and skip welding.

The clamping force of the electrodes; correct pressure and current make a sound resistance spot weld nugget.

The fused button of metal formed at a spot weld; its size indicates the joint's strength.

Dressing structural welds carefully without removing so much that the joint is weakened.

Welding heat and sparks can damage airbags, glass, and trim, so they are removed or shielded.

Properly aligning and gapping panels before welding so the weld has the right penetration and strength.

Makers specify number, size, and location of welds for a structural part; the repair duplicates them.

Cutting only where the OEM allows (factory seam or approved sectioning point) to keep the joint strong.

Structural welds must restore strength to spec; cosmetic welds (non-load-bearing) have less demanding requirements but still must hold.

Prevents welding current from finding a path through and damaging vehicle electronics and modules.

Identifying a plastic by its molded ISO code, a burn or float test, or maker info before choosing a repair method.

The standardized identification code molded into a part (e.g., TPO, PP, ABS, PUR) that tells the plastic type and repair method.

A plastic that softens and can be reshaped or welded each time it is heated, so it can be repaired by plastic welding or adhesive.

A plastic cured into a permanent shape that cannot be remelted, so it is repaired only with structural adhesives, not heat welding.

Thermoplastics can be welded (they remelt); thermosets cannot be remelted, so they are adhesive-repaired.

A common flexible thermoplastic used for bumper covers; weldable and repairable with the matching rod or adhesive.

A common thermoplastic for bumpers and trim; identified by ISO code and repaired by welding or adhesive.

A rigid thermoplastic used for interior and some exterior parts; weldable with matching rod or repaired with adhesive.

Polyurethane (often reaction-injection-molded) used in flexible parts; commonly repaired with two-part adhesives.

Joining thermoplastics by melting the base and a matching filler rod with hot air or an airless welder.

The filler rod must be the same plastic family as the part, or the weld won't fuse and will fail.

Mixing a resin and hardener to bond and rebuild plastic; common for thermosets and flexible covers.

Flexible adhesive is used on parts that flex (bumper covers) so the repair moves with the part instead of cracking.

Grinding a V into a crack from both sides creates surface for the weld or adhesive to bond and rebuild strength.

Embedding fiberglass cloth or metal mesh in the adhesive on the backside to strengthen a plastic repair.

Observing flame color, smoke, and odor of a small sample to help identify the plastic when no ISO code is present.

Some plastics (like polyolefins) float in water, helping distinguish them from denser plastics during identification.

A primer applied to certain plastics (like olefins) so adhesive or paint will bond to the otherwise low-energy surface.

Washing with soap and water, then a plastic cleaner, to remove mold-release agents and contamination before bonding.

Cleaning, sanding/grinding, and applying adhesion promoter as needed so the repair material bonds to the plastic.

It decides whether the part can be welded (thermoplastic) or must be adhesive-repaired (thermoset) and which materials to use.

Usually a flexible thermoplastic; repaired with flexible adhesive or welding and refinished with flex additives.

A rigid thermoset composite used on some panels; repaired with structural adhesives, not heat welding.

Reinforcing the hidden back of a cracked plastic part with adhesive and mesh before finishing the visible front.

An additive mixed into primer/paint so the finish flexes with the part and does not crack.

Many bumper covers and trim parts can be repaired more cheaply than replaced when the damage is repairable.

Too much heat distorts or burns plastic; welding temperature is matched to the plastic so it melts without scorching.

Removing material around the crack to bare, clean plastic and creating a bevel so the repair material grips.

Thermosets cannot remelt, so heat welding fails; they must be joined with structural adhesive.

Service information or the part catalog can confirm the plastic type when the ISO code is unclear.