A mount for OPD's printer. Square version goes into a .75 inch square hole, same that is both on the cabinet and the carts. (Old version an looks chunky.... I dont like it but it works lol) GMD cart version goes onto the thing that holds the GMD totes. It can be stuck on permanently with thick double sided tape. The nub has a tendency to break, reccommend making a couple extra just in case Required Hardware- Square Version 1x 1/4 inch nut 1x 1/4 inch bolt 1x 3mm nut 1x 3mm bolt - GMD Cart Version 1x 3mm nut 1x 3mm bolt* optional: 1mm thick double sided tape * length determines how far the nub sticks out.