ridge rib

noun

, Architecture.

1. a rib that runs along the ridge of a vault.
2. a stone or piece of timber placed at the apex of the gable in a vault or a timber roof.

Example Sentences

The chancel, a little lower than the nave and transepts, is entered by an acutely pointed and richly cusped arch, and has a regular Welsh groined vault, with a well-developed ridge rib.

From Project Gutenberg