Two employees were removing a sheave cover on a 310-ton crane in order to reeve the hook block. The hook block was located on stands 7-8 feet above the ground. One employee was removing a sheave cover from above while the other was removing bolts from below. The employee below was struck by the sheave cover and sustained fractured vertebrae, a fractured right ankle, an injury to the ACL and patella on the left knee, as well as a dislocated hip.