According to federal law, every garage door opener needs to include compliant safety features that match the latest standards in UL 325 (Underwriters Laboratories). If you want to test your reversing feature, you can perform an at-home test. First, test the balance (detailed above). If your door passes these tests, you can proceed to the reversal test.
Completely open the door and place a 1-1/2″ thick piece of wood (a 2×4 laid flat) near the center of the door on the floor. Once you’ve done this, press the wall button (or remote) to close the door. The door needs to hit the wood in order to reverse. If the door doesn’t reverse, it must be repaired or replaced, and soon. (Note that the bottom of the “one-piece doors” must be rigid enough to reverse when it comes into contact rather than close completely).