This is another style of hot wire cutter. An 8" length of 22 gauge nichrome wire is tensioned with eyebolts. The material is 1 1/4" thin wall PVC.

After rough cutting an opening for the window, the 2 x 4 studs act as a guide for the wire to follow to get a clean opening.

The basic hot wire cutter. This one has a 12" throat. The support board in front is used to support larger pieces. We use the same power supply. I'm a big fan of foot control.