It is a block of wood with a firm rubber pad that holds the file in place on the base edge bevel tool. I watched guys use a pony clamp and feel that after some practice this might be a little better. The fit is snug inside the tool. Once inside the SVST jig you can pick up the jig with the file under it in one hand just by holding on to the wooden block. Its not required but more like the cherry on top of your base bevel jig. Little expensive for what it does but the feel of it in your hand lead me to think I had better control over the stone and the jig while on the base.
