FLYRODDER has the fancy solution. For me, I just have some nylon twine, melted the ends until I had a mushroom head, and using a tautline knot at both ends, I was done.
Here's another idea (one that I have not made yet). Some yakkers like to fish unleashed/tethered while they have the rod in their hands and vice versa when they troll. To make this easier, I was gonna use the car key release that I get from the local hardware store for a couple of bucks. It's made of brass and is chrome plated. It looks like a cylinder with the two large split rings at both ends and you separate them by pushing a little spring loaded button on one end of the cylinder. Internally, pushing the button moves a shaft where a retaining BB can slide inward to allow the two pieces to separate. Hope you get the picture.