Universal Proximity Sensor Mount

This will let you mount a prox sensor (or anything really) anywhere you have a bolt on your X carriage facing up or down. For a prox sensor, the vertical part needs to be enough to hold the part just above where the hot end hits but below the sensor threshold. That can take some experimenting. If you hook the probe up to voltage you can adjust it using the red LED at the top.

With one bolt in the slot, it isn't super stable. I put washers under and over to clamp it. The probe doesn't take a lot of force, so it is OK but you probably couldn't use this for, say, a pen mount or anything.

Designed with OpenSCAD and the printer in the picture is a 5 year old Printrbot plus.