oarlock

From oar +‎ lock.

oarlock (plural oarlocks)

1. (nautical) A usually U-shaped device attached to the gunwale of a rowboat to hold the oars in place while rowing.

   Synonym: (UK) rowlock

   • 1906, Horatio Alger, Joe the Hotel Boy‎^[1]:

     But, as luck would have it, scarcely had he started to row his boat again when an oarlock broke, and so it took him the best part of an hour to make the trip.