Laser beam alignment tool for the cheap Chinese K40 40W CO2 Laser.
The tool has two parts, one for mounting on the mirror and one for mounting on the laser head.
Using tape or paper to mark positions has the problem of smoke residues getting on the mirrors and lens.
The tool protect mirror and lens from getting contaminated and has a holder for the test paper.
Instruction for the alignment process is well described and can easy be found on the net.