Admiralty drawings of smaller vessels often have keyhole-shaped features on the bulwarks which I have assumed are ports for sweeps. The example below is from ZAZ6116, the schooner Haddock, and there are six on each side. Am I right in my assumption that these are sweep ports?  The tables and drawings for sweeps in Steel https://www.thebigrow.com/?p=659#more-659 are quite extensive. For an 80 ton vessel he gives a total length of 25 feet of which 11 feet are inboard (handle plus loom).