I have a Prazi Chestmate. The packages advertises dovetails, mortises, box joints and dowels. I have an attached picture with three little black plastic pieces that are marked 3/8, 5/8 and 3/4. Does anyone know what they are? I have the instructions and the demo dvd and they are not mentioned. The product is discontinued by Prazi. Any help would be helpful. I found plenty of search items about how to use for dovetail but no mention of t he other uses.