Chamber flag
thingiverse
Insert this flag in your firearm's chamber for indicating it has been cleared. Simply print it out, then place it in the breach as instructed.
Download Model from thingiverse
With this file you will be able to print Chamber flag 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 Chamber flag.