The first time I tried to use mine, the clamp bolts failed under a 1200# load, though they were rated for 4000#. I had the thinh reinforced at a weld shop and have 1.5" bolts now. That sems to work. The original bolts were about 7/16".Clamp on forks are most efficient/effective when needing to move a partial pallet of dry chicken feathers.