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Now it's time to add tension to the spring. First, tighten the set screw located on the end of the spring onto the torsion tube. Next, thread the lift cable from the bottom of the door, up through the tracks, and insert it into the cable drum. Then, tighten the set screw on the cable drum by 3/4 to a full turn to remove any remaining slack in the cable. Repeat this process for both sides of the door. Consult the provided manual, specifically the 'Spring Winding Table C' (or similar chart), to determine the exact number of winds required for your specific door height. Using your drill and either the supplied insert bit or a 7/16-inch socket, tighten the spring according to the suggested number of winds. Finally, test the door's movement by hand to ensure it operates freely and easily; you should be able to lift it with only a few fingers. If you plan to use a garage door opener, make sure the door is properly reinforced to prevent damage when the opener is engaged. Refer to your opener's instructions for specific reinforcement guidelines.