Twin are also engineered to be used in pairs but only in a double strand configuration where both strands are clipped together in the belays. The two strands then work like a single rope but offer additional redundancy and higher resistance at sharp edges. For this reason, twin ropes are mainly used in alpine climbing, mixed climbing and ice climbing.
Twin ropes range from 6.9mm to 9mm diameters. Twin ropes are often even lighter and thinner than half ropes.
Twin ropes are tested in a double strand according to standard EN 892 with a test mass of 176lbs. (80kg). They need to withstand a minimum of 12 falls and the maximum impact force must not exceed 2,697lbs (12kN).
