Open the garage door. Lay the rubber water stop on the floor between the door tracks with the ramp-side of the stop facing into the garage. Use a straightedge and utility knife to cut the rubber stop to length, if necessary.
Lower the garage door until it makes contact with the rubber stop. Align the rubber water stop so the raised edge is against the inside of the door for the entire length of the door. Mark the floor along the edges of the stop with a pencil.
Scrub the area between the marks with a wire brush to make it easier for the adhesive to bond to the concrete. Sweep any debris and dust away from the marked area with a broom. Use a damp mop to remove any remaining dust, being careful not to remove the pencil marks.
Apply the included adhesive to the doorstop or concrete, according to the manufacturer’s instructions. Place the rubber water stop on the floor and align it with the pencil marks.
Lower the door until it contacts the stop. Adjust the stop until it is in the correct position and lower the door all the way to hold the stop in place. Allow the adhesive to cure for 24 hours before raising the garage door.