I created this helper to make sure my endstop jumpers were plugged into the correct pins on my Raspberry Pi. I use Octoprint to sense when the filament runs out. This was designed for my use, and I am sharing this in case someone else might find it useful.

The Makerbot 1.2 style endstop I got requires 3.3vdc, ground, and an I/O pin. This forces you to use Pin 1 (3.3vdc), Pin 6 (ground), and Pin 7 (GPIO 4).

There are many filament endstops cases and mounts available on Thingiverse.

I recommend you make sure the pins line up correctly before connecting the wires to your endstop. (I hooked up the pins in the wrong order once and it rebooted my Pi, I'm lucky I didn't wreck anything!)