This is an in-line anchor stop for my personal pontoon boat. The anchor rope flows through a pulley at the back of the boat. There is a tiedown cleat on the boat, but it's not in a convenient position to store the excess rope. This anchor stop stays on the line and you secure the stop in position by tying a simple overhand loop in the line and letting the knot slide into the countersunk hole. Make sure you tie the knot with the slack end of the line forming the loop. To release the stop, slide out the knot and pull on the slack side of the line to release the knot.

This stop will work for kayaks, pontoon boats and small rowboats. I am not sure it's strong enough for large boats.

I printed it in PETG (outdoor use) with 4 perimeters and 50% gyroid infill for strength.

I used the Knurled Surface Finishing Library (http://www.thingiverse.com/thing:9095) to create the outside knurl. It's a SCAD program that allows full customization of cylindrical knurls. The models take a while to render, but it's a GREAT program. Thanks to aubenc @ Thingiverse for creating it!