[Techgenie]’s handheld hot wire foam cutter is a simple build based on a single 18650 and a piece of nichrome wire. While this is probably not the most Earth-shattering hack you’ll see today ...
While there are all sorts of ways to build a hot wire foam cutter, this design from [jasonwinfieldnz ... One nice touch is the simple fence that rides along two slots and secures with wingnuts.