Step inside the shower booth and slide the glass door into the center position.
Lift the bottom part of the door toward you. Lift it up so that the wheels on the upper track are displaced from the track. Use the Phillips screwdriver to dislodge the door from the rail. Lift the door up carefully and ask someone to help you carry the glass outside the shower.
Scrape away the old caulk from the tracks, using a putty knife. Clean the rails thoroughly. Apply new caulk on the rails with the caulking gun and let the caulk dry for three hours.
Stand on the outside of the shower booth. Lift the new glass shower door. Lower the rollers on the top of the door onto the top rail of the shower booth frame. Angle the door so that the bottom part of it fits into the bottom rail.
Fasten the glass door into the rails, using screws and the screwdriver.