Materials:

• 5 feet of 1×10 board, cut into one 35 inch and one 25 inch length. We chose poplar because it was smooth and straight. Will probably sand the edges round at some point.
• 4 6×6 L brackets bolted together in pairs
• A length (maybe 9 inches or so) of 2″ inner diameter PVC pipe, cut (ripped ghetto style with a hacksaw in the garage) in half lengthwise
• 4 ¼-20 ¾ inch bolts with nuts
• 16 ¼-20 1½ inch bolts with nuts
• A drill with a ¼ inch bit, preferably already owned

Go to the hardware store right before close and get dirty looks. Pay $50. Go home. Mark some lines and circles. Drill holes. Tighten nuts. Put a piece of felt inside the PVC pipe between the bolt head and the treadmill arm on each side. The end.