1. You can use mechanical means instead of wheel chocks or blocks to secure the trailer to the loading dock.
2. Wheel chocks or blocks are not required when:
a. The mechanical means prevents the trailer from moving away from the dock.
b. The mechanical equipment is used and maintained as recommended by the manufacturer.
c. Damaged mechanical equipment is immediately removed from service.
You may need to use fixed jacks to keep a semi-trailer that is not coupled to a tractor from up ending during loading or unloading.