Abstract: Employee #1 was working at drilling rig #11 located northeast of Cheyenne, OK. He was going under a derrick mast as it was being lowered to catch a boom pole that was on the other side of the mast before it dug into the ground. Two other employees were in the area. One was directing the lowering of the mast, the other was helping Employee #1 keep the boom pole on this side from also digging into the ground. The ladder safety device counterweight was not secured in the derrick. Just as Employee #1 was passing under the mast, which was within 24 inches of being placed onto the headache rack, the counterweight fell and struck him on the side of the head. Employee #1 died from his injuries. At the time of the accident, the wind was blowing hard and the laydown crew was at least two men short. All the men involved in this accident had several years of experience in the oil-drilling industry.