My sailboat's mooring lines were getting frayed due to rubbing over the aluminum toe-rail, and I didn't care to install a standard deck chock as that would require drilling holes into the deck on the boat. This design snaps onto the toe-rail, and can slide back and forth to adjust to the correct angle for mooring at various slips and mooring floats. It is designed for 3/8" (10mm) mooring line.

I printed this in PETG and the slight flexability allows it to snap firmly onto the toe-rail without causing stress cracks. Will have to wait and see how this survives being exposed to the weather, but as it doesn't receive much force other then compressive, I don't think that a little UV degradation will cause too much harm.

This is designed for a 1" (25mm) high toe-rail (top rail diameter 7mm, web thickness 4mm). I've tested it on a San Juan 24, J-24, C&C 30 and Olson 30.