lock core holder (customizable)

Customizable lock core hand holder. This was strongly influenced by https://www.thingiverse.com/thing:1386781 with the following improvements

1. Optional cutaway for cut away locks (note if yours is cutaway on the other side just mirror the part in your slicer.
2. Extra room in the back to allow the unlocked cylinder to rotate freely when pushed all the way into the holder.
3. Set screw is now 6-32x1/4" (a plus or a minus), which is the most common size "coarse" computer screw, so you sho