If a tolerance zone is toleranced by two parallel straight lines or planes, it is referred to as slope tolerance (slope for short).
The toleranced object must lie within the spanned tolerance zone with a given distance.
For example, the axis of a hole is toleranced so that its axis must lie within a cylinder with a given distance.
If an inclined surface is toleranced, it must lie at the given distance between two planes.
This glossary of plastic industry is provided by PLEXPERT Canada Inc.