Cribbing and Stabilization Fundamentals

Why Stabilization Comes First

Before any rescuer or medic touches a patient trapped in a vehicle, that vehicle must be stabilized. A shifting car can crush a rescuer, worsen a patient's spinal injury, or trap tools at a critical moment. The rule is simple: stabilize, then access. No exceptions. Vehicle stabilization is a foundational skill tested under NFPA 1006 (Technical Rescue Personnel) and practiced on every extrication call regardless of how minor the crash appears.

Understanding Vehicle Movement

Crash vehicles can move in three ways: rock (forward and back), roll (side to side), and bounce (vertical spring from suspension). Step chocks and wheel chocks resist rocking. Box cribs resist rolling and settling. Struts resist roll and lateral shift on side-lying or inverted vehicles. You must address all three movement types before calling a vehicle stable.

PPE and Scene Safety

Don full structural firefighting PPE for every stabilization lab: helmet with face shield down, structural gloves, and safety boots with ankle support. Eye protection is required when cutting or hammering cribbing. Establish a hot zone around the vehicle — only the crew performing stabilization enters. Keep bystanders and unnecessary personnel outside. Before approaching, check for fuel leaks, deployed airbags, hybrid/electric system indicators, and unstable terrain. Call out hazards to your crew.

Cribbing Materials and Their Roles

4×4 lumber is the workhorse of vehicle stabilization. Stacked in alternating layers of two pieces each, it forms a box crib — a hollow square stack that distributes load over a broad footprint and resists compression from multiple directions. 2×4 lumber is used as wedges to fill gaps and eliminate play (movement) between crib layers and the vehicle body. A wedge with any gap is not doing its job; drive it until snug.

Step chocks are pre-fabricated plastic or wood wedge assemblies that slide under a vehicle's rocker panel or axle area. They are fast to deploy and resist both rocking and rolling on upright vehicles. Always place step chocks on firm, level ground when possible, and pair them with wheel chocks placed fore and aft of at least two tires to prevent the vehicle from rolling off the step chocks.

Telescoping struts (also called rescue struts or Paratech-style struts) are adjustable metal poles with swivel feet. On side-lying or inverted vehicles, struts are deployed in pairs or triplets at angles to form a rigid triangle against the vehicle body, opposing the direction of potential roll or collapse. Secure struts with ratchet straps or stake pins per the manufacturer's instructions — never rely on friction alone.

Stabilizing an Upright Vehicle

1. Size up the vehicle: note suspension height, tire condition, and whether the engine is running (shut it off if safe to do so).

2. Place wheel chocks fore and aft of both rear tires (or all four tires if the vehicle is on a slope).

3. Slide step chocks under the rocker panels on both sides, large end toward the vehicle, until firm contact is made. Drive a 2×4 wedge into any remaining gap.

4. Perform a push test: apply firm hand pressure to the roof and each corner. No rock, no roll = stable. Call "stable" only after the instructor confirms.

Building a Box Crib for a Side-Lying Vehicle

A minimum three-point crib system is required for a vehicle on its side: one crib at the front (engine compartment area), one at the rear (trunk/bumper area), and one at the center (door/rocker area). Each point must independently support and resist roll.

To build one box crib station: lay two 4×4s parallel, roughly shoulder-width apart. Cross two more 4×4s perpendicular on top (alternating layers, like a log cabin). Continue until the stack reaches the vehicle surface. Drive 2×4 wedges into any gap between the top layer and the vehicle until the vehicle cannot rock on that crib. The vehicle roof or underside rests on the crib — never on a single point.

After all three cribs are in place, team members apply simultaneous push tests at the top and bottom of the vehicle. If movement is detected, add wedges or adjust crib height before proceeding.

Stabilizing an Inverted Vehicle

An inverted (upside-down) vehicle is inherently unstable because its roof — not designed as a load-bearing surface — is now on the ground. The vehicle may collapse inward as rescuers work.

Deploy telescoping struts at a minimum of two points, angled outward from the vehicle's bottom rails (now facing up) to firm ground. Set the swivel foot flat on the ground and extend the inner tube until the strut head contacts the vehicle frame or rocker rail solidly. Lock the strut per the manufacturer's procedure. Add box cribs at the corners (between the vehicle's roof-on-ground and the strut anchor points) to prevent sudden drop if the roof gives way. Secure with ratchet straps as indicated by your department protocol. Document your crib configuration on the sketch sheet before moving to patient access.

The Push Test and Calling Stable

The push test is your objective verification tool. The instructor applies firm, deliberate force to the vehicle from multiple directions. The tolerance is zero perceptible rocking or rolling. If the vehicle moves, you are not done. Add cribbing, tighten wedges, reposition struts, and test again. Never call "stable" until the push test is passed and the instructor confirms. Premature declaration of stability is a patient-safety and rescuer-safety failure.

Lab Log and Sketch Requirement

For every skill station, record the crib configuration on your sketch sheet: label each crib or chock point, note the number of layers, and indicate strut angles for the inverted station. The sketch is part of your lab pass/fail record and trains you to communicate your setup to incoming crews at a real incident.