A heavy structural bracket or trunk mounted on the deck that holds the base of a mast and incorporates a heavy pivot pin. It allows the entire mast to be folded down horizontally to clear low bridges or overhead power lines, and then raised back to vertical without needing a crane. It is highly common on canal boats and coastal cruisers.
Heard on the job
Pull the locking pin on the tabernacle so we can drop the mast before we hit the bridge.