A wedge or similar device inserted in a space adjacent to an object, to hold the object steady.  Any place you see workers around a stopped truck, you may see a chock placed near the rear wheel.  OSHA requires that work vehicles be chocked. OSHA compliant truck chocks are required.

OSHA requires drivers to set the brakes and that workers chock the rear tires of trucks before they are loaded or unloaded. If a driver detaches a trailer from his truck he must stabilize the trailer with jacks and chock the rear wheels.

Using OSHA Compliant Truck Chocks is a great practice.  The old block of wood is being replaced by modern, completely compliant, visible chocks.

The OSHA directive and guidance for chocking is 29 CFR 1910.178(k)(1) and (m)(7): Mechanical Means to Secure Trucks or Trailers to a Loading Dock

Reviewing this guidance for chocking a truck when it is being loaded or unloaded.  Remember that government agencies like OSHA update guidance directives from time to time.

Chocks are not what they used to be.  The old wedge of wood is still around but modern truck wheel chocks that are clearly visible by workers are now the norm.

The purpose of chocking a truck is to prevent a truck from being able to back up inadvertently.  Trucks should be fully braked before the chock is inserted near a wheel.

The modern wheel immobilizers are corrosion-resistant, spark-resistant (static electricity) and powder-coated for a very long life.  Modern chocks keep your loading/unloading operation OSHA compliant.  These are the best wheel chocks for trucks.

Worker safety in any loading-unloading area should be the number one priority.  Visible, static resistant chocking in fuel loading areas should be a robust practice for all hands.  Modern chocks can be folded and stored in truck compartments and in areas near a loading/unloading area.

OSHA compliant truck chocks
OSHA compliant Truck Chocks