The completed panel cutter in use. See how to build it below.

Cut a piece of 3/4" thick sheet material that's approximately 24" wide by 36" long. You'll also need a strip of hardwood that fits snugly, without binding, in one of the miter slots on your table saw. The hardwood strip should be about 30" long so a few inches will extend past the front and rear edges of the sheet material. Most miter slots are 3/4" wide and about 1/4" to 3/8" deep.

Attach the hardwood strip to the bottom face of the panel, parallel to one 24" long edge. Draw a line parallel to the edge to guide the strip placement being sure to set it back so there's 1" of panel extending past the blade.

Place the panel, with the hardwood strip attached, in the miter slot and cut the panel overhang. This cut will align the panel jig miter strip, and the edge closest to the blade, parallel to the saw blade.

Use a carpenter's framing square to align a hardwood guide at 90-degrees to the panel's cut edge. Secure the guide with screws.