How do you make the key to attach a figure 8 to a canyoneering belay? We thread the rope through the figure 8 in the largest loop, pass it over the bottleneck, then take the protruding end, thread it back through the large hole, and then wrap it around the smaller hole.

This system is unrestricted; that is, if someone asks for rope, I remove it, and when someone is hanging, holding it allows the rope to slide. Then, when I decide the rope is enough, I can redo the key.