Use this compact slitter for cutting packing tape, opening bags, or slicing through shrink wrap. It uses the ubiquitous #11 X-acto knife blades, so you can always have a new sharp edge. The tip is always covered and the gap is narrow, so it is safe to keep in your pocket.

The blade slides in through a slot in the back and then drops down into a pocket. You then use a 7mm long piece of 1.75mm filament (shown in red in the photos) as a plug to hold the blade in place. To remove the blade, poke the plug back out with a paperclip and then use the paperclip in the oval slot to tease the blade back out of the pocket.

Print in the orientation provided and without supports. Use a 0.4mm nozzle (or smaller), and print with a 0.2mm (or less) layer height.

Note: This version is a significant redesign of my original posting that improves the attack angle of the blade.