Tying up a boat is a common practice used to secure the vessel in a particular location. It involves using a rope or chain to attach the boat to a dock, pier, or other structure. The term 'tie up a boat' can also refer to the act of tying the boat's bow and stern lines together, which is known as 'putto' (5 letters) and 'MOOR' (4 letters). This technique is used to keep the boat from drifting away while it is not in use.