This is a 3x4 Gridfinity baseplate for the Gridfinity Ultimate Drawer System remix.
It can be fastened to the top of a rack with 4x 5mm M4 capheads and 4x nuts.
Please note that the baseplate is two directional. If it isn't sitting centred on the rack when you go to fasten it down, spin it around 180 degrees (on the Z axis) and it will.
The author remixed this model.