The water supply lines must already be in place between the joists under the floor.
1.1. Determine where on the floor the supply lines are located.
1.2. Mark out an opening of approximately 7″ x 7″ on the floor.
1.3. Drill a hole in one corner to insert the jigsaw blade. Cut out the opening with the jigsaw.
1.4. Determine the height of your faucet spout, remembering to account for the height of the finished floor.
1.5. Screw down a 6″-wide wood support, 2″ to 3″ below the floor surface. Adjust according to the height of the faucet base, and make sure that the mounting flange (escutcheon mounting plate) is level with the finished surface of the floor. The wood support should be at least 2″ thick.
1.6. Lower the faucet onto the support and turn the spout to the inside of the bathtub.
1.7. Check and adjust the distance of the spout in relation to the tub.
1.8. Once you have noted down these measurements, temporarily mount the whole faucet (and its base) with screws and washers. Tighten only slightly.
1.9. Check that the hot and cold water supply lines are aligned with the inlet connections on each side of the base. If they are not, make the necessary modifications to lengthen or shorten the supply lines.
1.10. Test the handle to make sure that full rotation of the spout will not interfere with the tub or the wall.