Looking for a way to have an adjustable inline stopper on a piece of running rigging (3/8" three-strand rope) that will allow easy loosening and secure tightening.
This is for a control line that passes through a bulkhead and the idea is to be able to loosen the stopper to slide back and forth to adjust and then tighten back down so that when said control line fetches stopper against the bulkhead it jams and prevents further movement in that direction. The forces involved are not huge; it's a steering line not a sheet or halyard but I would like it to be pretty secure. While there is enough slack in the line to allow a small loop to engage with a stopper in some way the line does not have enough slack in it to allow an actual knot to be tied into it nor would I want to; neither end is free. The stopper would need to be something that could be tied around the line like a prusik knot or similar.
I thought of a way to do it with a wood toggle but would prefer using some type of knot if possible as the stopper rides along a varnished surface. Any ideas?