A projection used for strength or for attaching to another object WordNet 3.0 & Open English WordNet

A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength ; for easy attachment/transfer of contact force with another object ; or for stabilizing and guiding the movements of a machine or its parts. Wikipedia

Ridge, a rib or rim. Wikipedia Disambiguation

External or internal ridge, or rim which provides strength Wikidata

An external or internal rib or rim, used either to add strength or to hold something in place. OmegaWiki