California Labor Code
Every dock plate shall be constructed and maintained with strength sufficient to support the load carried thereon.
Dock plates shall be secured in position when spanning the space between the dock or the unloading platform and the vehicle. The dock plate, together with its securing devices, where used over spans of different lengths, shall be of such construction as will readily obtain rigid security over such spans.
The dock plates shall be so constructed and maintained that when they are secured in position the end edges of the plate shall be in substantial contact with dock or loading platform, and with the vehicle bed in such manner as to prevent rocking or sliding.