Catapult
thingiverse
You are advised to purchase a sewing needle, so that it can be activated by a tripwire. This catapult can be used as a security system for a locker.
Download Model from thingiverse
With this file you will be able to print Catapult with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Catapult.