These are the printed parts to make adjustable-height feet to attach to the ends of the 2040 horizontal extrusions of the base frame of a Robotdigg SCARA printer. The printer needs 3 of them. The other parts you need are need three M6x30mm socket cap head screws (or one M6x30 for the foot and two M6x20 to attach it to the extrusion), two M6 nuts and a M6 thread tapping tool.
Remove the end caps from the extrusions and use the tapping tool to thread the two central holes to the length of the fixing screws less 5mm, then secure the larger printed part to the extrusion using two screws. Also thread the central hole of the round foot, then screw a M6x30mm cap head screw into it from the bottom until it is tight. Put a nut on the protruding screw end, then insert this into the underside of the other printed part so that the nut fits in the nut trap. Add another nut on the top side to finish off.
See my blog entry at https://miscsolutions.wordpress.com/2017/08/09/testing-the-robotdigg-scara-arm-3d-printer/ for how to strengthen the base frame of the printer.