This is to keep from accidentally flipping a toggle switch. In this case I intend to use it with a 1/2 hp 90V DC Permanent Magnet motor to control the rotation direction, if it is running and accidentally switched - bad things may happen to the motor or motor control (the magic smoke may get out of the wires).
This is for a toggle switch with a 12 mm stem and 16 mm nut (turned out to be 15 mm nut). In my case this is a NKK Toggle Switch S332T-RO.
There is clearance to put a deep well socket down over the switch stem to tighten the nut. The action of the switch would be aligned with the notches so it can be reached with finger tips. The 2 side holes near the bottom are for a pair of set screws to hold it from twisting on the shaft of the switch.

Print flat side down and clean up as needed. The 2 side holes in the base are to be tapped for #6-32 set screws to keep it aligned with the toggle switch.