Switching out nozzles on the Printrbot is a bit of a pain because you have to re-adjust the Z-axis set screw to raise or lower it accordingly. I wanted to have a nylock nut permanently held in position to provide tension on the screw so I didn't have to loosen and tighten nuts against the screw all the time.
Step 1) Print!
Step 2) Insert a #6-32 nylock nut in the hole inside.
Step 3) Attach to Printrbot!