Things You'll Need
1/8-inch drill bit
1-inch waterproof screws
Installing a shower door over a fiberglass shower is the easiest type of shower door to install because there is no need for additional anchors or masonry bits like there is for concrete or tile installation. With a fiberglass shower all you have to do is screw in the shower door and seal it in place.
Measure the base of the shower doorway so that you can determine the length for the bottom shower door track. Put on your safety glasses and use the hacksaw to cut the door track to match the correct measurement.
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Place the door track in the middle of the bottom door frame of the shower. Make sure the taller side of the track faces the outside of the shower. This will prevent water from leaking outside the shower and onto the floor. Tape the track against the shower base with masking tape. Mark the placement of the track with a pencil.
Slip the wall channels into the bottom door track. Align the channel with the edge of the shower door frame and mark the placement of screw holes with a pencil. Repeat for the other wall channel on the other side of the shower.
Drill a hole into each of the pencil marks along the shower door frame for the wall channels and for the bottom door track.
Apply a line of silicone sealer to the bottom of the wall channels. Press them against the wall then screw the wall channels into the holes you drilled into the fiberglass shower. Screw in both wall channels and the bottom track in this manner.
Measure the distance between the wall channels at the top of the shower. Cut the shower header to equal this measurement. Slip the header over the wall channels to complete the shower door frame.
Attach the shower door to the frame using the enclosed hinges and screws. Make sure the seal between the shower door and the shower itself is tight so that no water can escape during a shower.
Add any additional silicon sealer around the shower frame to create a watertight seal between the inside and the outside of the shower. Allow the sealer to sit for 24 hours before using the shower.