First, it drags the ring off of the glider and second, it reduces the likelyhood of the line ending up in a tangled pile. This amber colored material can be obtained from a medical supply house. This is the stretchy rubber stuff - not the clear plastic and not the synthetic black rubber. 250 feet of polyester or nylon cordage. Something a little stronger than kite string such as nylon cordage for tying boxes is suitable.
Key rings are suitable for light duty use.
One eight inch spike. A second spike can be used as an axle for the reel instead of a dowel. A large washer with an inside diameter to fit the shank of the spike. This is to keep the ring from slipping off of the end of the spike. A small, simple parachute.