The lanyard for a boat's bell can be a simple length of rope, tied to the bell's clapper--or it can be a properly nautical piece of fancy ropework called chain sennit, or monkey braid. The chain sennit is similar to the way electrical cords are tied, that is, a series of slip knots that are readily untied when one end of the cord is pulled. The difference is that the chain sennit has a secured end that will tighten when pulled. This makes it appropriate for decorative applications that require stability.
Tie a figure-eight knot in the end of the rope and feed the unknotted end through the hole in the bottom of the bell's clapper, then make a loop in the rope--a noose--on the side of the clapper opposite the figure-eight knot.
Form a loop in the rope and tuck it through the noose, then form another loop, tucking it through the first, and pulling the first loop tight. Repeat, pulling each successive loop tight.
When you reach the end of the rope, do not make a loop. Tuck the end of the rope through the loop and pull the end to tighten the last loop.
The end of the chain sennit can be finished with a decorative knot, like a Wall and Crown knot, if the rope is long enough.