 The lack of available technical equipment during the war forced Chevalier and his team to innovate and develop their own.The scaling-pole (1940), nylon ropes (1942), use of explosives in caves (1947), and mechanical rope-ascenders (Henri Brenot's "monkeys", first used by Chevalier and Brenot in a cave in 1934) can be traced historically to the exploration of the Dent de Crolles cave system.In the late 1950s, American caver Bill Cuddington, developed the single rope technique (SRT) in the United States.