This is a safety box cutter. The design allow the user to extend the blade while holding the knife. Once letting go of the handle, the blade will automatically go back inside so you can't cut yourself (but please still be safe with the sharp blade).

BOM:

• Printed parts
• 5x M3*10mm screws
• 2x M3x5mm screws
• 2x M3 washers
• 19mm wide blade

Assembly:

• Place and screw the blade onto the blade holder with an M3x5 screw and a washer (about 10mm of the blade should overhang).
• Add a rubber band between the end and the middle of the housing, where you need to secure it with an M3x5 screw and a washer.
• Add the handle to the bottom.
• Screw everything together.