Jim Mills is screwing fuses into rounds. He is fusing point detonating fuses (PD), in front of rounds not yet fused. Behind him a few rounds with black fuses, are time fuses. They are used to create an air burst. If the fuse is set for say 1 second, the round blows up 1 second after it is fired from the gun, raining shrapnel down on an enemy position. They were especially useful when we were in direct contact with the enemy, and the gunner could line up the enemy in the sight. The trick then was guessing the right time. A good gunner could adjust on his target within a couple shots, and put one directly above it.
Another type of fuse we used was the Variable Time (VT) fuse. These we used also to get an air burst at a more distant target. The variable time fuses were temperamental, and I remember them blowing up prematurely during rain storms.