16mm CO2 Laser Alignment tool

This is a "reverse alignment laser" that you can use to align a CO2 laser mirrors starting at the end furthest from the tube.

CO2 lasers are invisible IR so you usually use a "scorch test" where you stick some tape in front of the mirror (not on it) and turn the laser on till a black burn appears. You adjust the mirrors one at a time starting at the laser tube till the laser is burning in the same spot regardless of the position of the moving mirrors.

This tool works the same way except you start at the mirror furthest from the tube. Because the beam is visible its safer and you don't have to keep opening the lid to adjust or see something.

You can buy these and they aren't too expensive and are accurate when they arrive! I recommend you buy one of these.
https://american-photonics.myshopify.com/products/k40-reverse-laser-alignment-nut

You can buy a “boresight laser” and easily make your own, these boresight lasers cost about U$12-20 online and I think that's what APC uses