In this video, This Old House general contractor Tom Silva explains how to fix a sticky shower door.
1 Use screwdriver to loosen the screws in each corner of the shower doorframe.
2 Loosen the screws holding the handle to the shower door.
3 Open the shower door and stand a 2x4 block underneath its outer, bottom corner.
4 Slide shims into the space between the 2x4 block and door.
5 Hold a wood block against bottom corner of door and tap upward with hammer.
6 Drive shims in tight to prevent door from sagging back down.
7 Repeat: tap up on door corner, drive in the shims.
8 Tighten all the doorframe screws and handle screws; close the door.
9 If the door still sticks, loosen the screws and repeat the process.