EE was working on a BMR(crusher) liner bolt replacement. Crew was placing the top lid on the BMR. 2 cranes/hoists are used to move the lid. The first positions the lid approx 3' short of its final placemen. The lid was placed on top of the BMR while the second chain hoist was rigged. While resting on the machine, the lid teetered and fell approx 18"" on a mechanics foot.