Replacing 3-ways on dump chains and the bridle pins (1 3/4"" x 9"") He picked the bridle pin (with the top ""keeper"" in place) up with his right hand, by the top(above the ""keeper"") He started to drop it into the hole, his left hand was next to the hole, the bridle pin slipped out of his hand and left thumb was caught between the pin keeper and the clevis.