I needed a way to attach a piece of glass (4mm thick in my case) the same xy dimensions (225mm x 225mm) as my platform below it (mdf) without cutting holes into the glass.These are holders to do such a thing.There are spots for m3 screws to level into and the glass slides into the sliders, with smaller m3 screws to secure it tight.Stl files may be useful if you have pretty much the same setup with a 4mm glass and the same screw size. If not, you can use the scad files to edit.They are slim so that they don't rub up against the threaded rods on a mendel/prusa type. Print a set of ( Top + Bottom ) x 4,Use your m3 screws holding the bed to go inside the bottom holder. You will need to undo any springs etc first. Use a smaller m3 screw and nut to secure the glass in place.These are designed so they don't need to go over the x edge, as not to hit threaded rods.