Folks use these to attach (belay...) the halyard on Nutshell Prams, Shellback dinghies, and other small boats. So, what that means is, instead of a cleat to tie-off the line which you use to raise your sail and keep it raised, you can use a belaying pin. Drill a hole in the thwart (seat) and put the belaying pin in that hole. When you've raised your sail, you'll wrap the line around the upper and lower (the shaft that sticks-out below the thwart) parts of the pin in that standard figure-eight winding, to secure the sail. Two slick things about this: if you are rowing instead of sailing, you simply pull the belaying pin out, and it's not in your way. AND, if you get caught in a bit more wind than you wanted, and need to reduce sail area immediately, you can grab the top / handle part of the belaying pin, and pull it out. This releases the line, and your sail will drop down (watch yer noggin') very quickly. No fussing with un-wrapping from a cleat.

Made from Rock Maple (the really hard stuff), turned pin approx. 8" long, the handle length is 3 1/2", and the shaft of the pin is 4 1/2" long, with a 1/2" diameter shaft. Just the right size for your small boat.