Disconnect the opener, lift the door manually—it should stay open at 3–4 feet. If it drops or rises unevenly, adjust spring tension (caution: springs are dangerous—consider a pro).

Wrap the end tightly with duct tape before cutting, then seal with a flame (for synthetic ropes) or dip in wax (for natural fibers).

Tighten hinge screws first. If the door is misaligned, shim the hinges or file down the latch plate hole slightly.