This is a system to mount things using screws on slotted mdf boards.

Screw_holder2.stl: Normal fit, gap 11 mm, internal slot front 30 mm, internal slot back 31 mm
Screw_holder_loose.stl: Loose fit, 1 mm less from the normal one
Screw_holder_wide.stl: Wide one, 2 mm more from the normal one

You can use a screw/nut combination or a wood screw. Any self tapping wood screw will hang very strongly to it.