This is a clever bench dog. Whenever you need it, simply press the top and up it pops (about 8mm projection). When you are done, just press down to recess the stop back into the hole. The solid brass body has a 2° inward slope to hold the wood securely. The spring mechanism is height adjustable to accommodate hole depths of between 50mm and 62mm with a diameter of 3/4"(19mm). For deeper holes, use a dowel spacer. When used in a through hole, the dog sits on a steel plate screwed to the underside of the worktop. Additional stop plates are available in a package of four to allow you to set up additional bench locations. Sold in pairs, Made in Canada.