I've been asked a few times in the last couple months to describe the sinew comb that i use to process my back sinew. The comb i use is made from two 4 inch pieces of 1 x 2 inch pine. There are two rows of holes drilled through one of the pieces of pine so that i can drive several finishing nails through it. To keep the nails from sliding out, i screw the second piece of pine to the first so that it sandwiches the heads of the nails between them. Here are a couple photographs:
http://www.uvm.edu/~egarza/Comb1.JPGhttp://www.uvm.edu/~egarza/Comb2.JPGI change the nails before each hunting season, and they get pretty bent up by the time i'm finished with a season's sinew. And this is when processing back tendons, which are relatively gentle on the nails. If you were to process leg tendons, you'll either have to change the nails more often or use stouter nails. I clamp this in a vice to use it.