Strung across Calle Purisima was a wire. On the wire were bobbins with ribbon wrapped around them. At the end of each ribbon was a small white plastic ring.
The contestants then rode along on one of two old bicycles and tried to catch the rings with a tapered wooden stick. Once the participants had caught the ribbon they exchanged it for a sash worn by the fiesta queen or dame whose name was printed on it.
It sounds hard and it was. It required excellent bike handling skills and a steady aim to capture the rings. You can see how well they did in my photos here.