The sliding deadman's job is to support long boards on edge by either resting the board on a peg or a hold fast. To make mine, I flattened a pine 2" x 8", and rabbeted the top, 5/8" from the front. There is a matching groove in the bottom of the benchtop that is 5/8" from the edge, and 5/8" wide. It is also 1/2" deep, which is the deepest my plow plane goes. This poses a slight problem, as most plans I've seen have the deadman come out by deepening the groove, and having it slide up and then over the bottom. This is why I made the tongue removable, by two screws, I didn't want the tongue to be less than 1/2" long. The bottom track is shaped like a 'v', if I had made a groove, it is likely that sawdust and shavings would have collected in the corners, and not allow the deadman to slide. The bottom 'v' groove was very hard to make, I chopped it out with a chisel, and other tools.