Bottom Sweep
The seal that runs along the bottom edge of a shower door, closing the gap between the glass and the shower pan or tile floor.
A bottom sweep is a rigid vinyl strip with a soft flap (or a small drip rail) that clips onto the bottom edge of the door glass. It's the single most common shower door seal replaced, because it sits in standing water and UV-heavy conditions every day and hardens or cracks faster than any other seal on the door.
Bottom sweeps are sold by glass thickness (1/4", 3/8", 1/2") and by length — most come in a standard 3-foot (36") strip that you trim to width with scissors or a utility knife. They snap onto the glass edge; no drilling, no adhesive on most designs.