Cut two pieces of pressboard using a circular saw to measure 18 inches wide, 72 inches long.
Sand the edges of the two boards using fine-grit sandpaper to make them smooth.
Place the two pressboard side by side on a flat surface. Line the edges up evenly.
Place three hinges along the seam where the two pressboards touch, then screw the hinges in place with a screwdriver and 1/2-inch screws. Position the hinges out evenly with one at the top, middle and bottom of the board.
Screw a track knob onto each end of the pressboards, positioning each knob 2 inches from the corner and facing either up or down, respectively.
Screw a knob handle onto the front of one of the pressboard panels, positioning the knob 2 inches from the edge and centering it along the edge. You can now insert the handmade bi-fold doors into a track.