Step1: Cut It
1. First of all, when you're making a replacement panel, you're going to start out with a stock sheet of steel, and it will need to be cut down. To make nice, clean, straight-edge cuts, an air shear will get the job done. Measure out your sheet, place the metal into the shear, and line it up with the blade, then release the shear, and voila, you have a new straight-cut edge.