the initial dots were made of glass and were attached to the road by nails or tacks, as suggested by botts. the nails were soon abandoned: his team discovered that when the dots popped loose under stress, the nails punctured tires. contrary to a common myth, the published record does not make clear whether botts invented the famous epoxy that solved the problem; some sources indicate that one of his protégés was responsible for the epoxy. in september 1966, the california state legislature mandated that botts' dots be used for lane markings for all state highways in all non-snowfall areas.