Trunnion:
A trunnion (from Old French trognon ‘trunk‘) is a cylindrical protrusion used as a mounting or pivoting point. First associated with cannons, they are an important military development.
In mechanical engineering (…), it is one part of a rotating joint where a shaft (the trunnion) is inserted into (and turns inside) a full or partial cylinder. [Wikipedia]
Well, noted near the end of this Cruising the Cut video.
