A few core terms appear repeatedly in technical shower-door documentation. When everyone uses the same terms, measuring and troubleshooting become much easier.

Out of level

This refers to the horizontal plane—such as a curb, floor, sill or tub deck—being off level.

Out of plumb

This refers to the vertical plane—typically a wall, buttress or step-up—leaning inward or outward.

Bowed wall

This means the wall is not straight. It may curve in, curve out, or have several waves along its height.

Why the distinction matters

A wall may be out of plumb and still be manageable if it is straight. A bowed wall is much harder because the glass edge is straight while the wall surface changes repeatedly.