Materials
Cribbing is usually accomplished with blocks of wood, often 4"x4" or 6"x6" and 18"-24" long. Soft woods, like spruce and pine are often preferred because they crack slowly and make loud noises before completely failing, whereas stiffer woods may fail explosively and without warning.
Cribbing may also be made out of plastic, which unlike wood is not susceptible to rot or corrosion from fluids the cribbing may come in contact with (e.g. oil, gasoline, hydraulic fluid).
Cribbing equipment is normally of three varieties: rectangular blocks, wedges (also called shims), and "step chocks" (large wooden chocks constructed of wood of different lengths). Blocks are the bread and butter of cribbing and will be used in most cribbing evolutions. Shims are used to snug up contact between the crib and supported object or change the direction of the crib (tilt). Step chocks are often used as a quick solution for stabilizing vehicles on all fours or to quickly increase the height of a crib.
Read more about this topic: Box Crib
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