Made a hot wire cutter for some 2.4m x 1.2m x 50mm sheets of polystyrene. I used a cheap ATX power supply, wired it to run without being connected to a PC, and used it to run about 75w through some nichrome wire that I've got rigged up with steel springs for tension. One spring attaches to my garage door when it's in the open position (above my head), and the other spring attaches underneath a workbench. Off-the-shelf hot wire cutters can't handle the depth of cut I need to make, so I had to DIY it. I'll be using the polystyrene to insulate a new coal-bunker-wormery, the roof of the garage where it catches the sun and tends to bake the garage in the summer and maybe a few tanks outside.