Abrasion is one of a rope's worst enemies. Rock, carabiners and belay devices can all be a major source of friction and cause wear and abrasion along the whole length of the rope. The individual sheath fibres tear and the sheath's surface gets rougher. As a result, the sheath gets thinner, and the rope becomes rough and furry. Once the core becomes visible, the end is nigh. The greater the load, the rougher the rock and the sharper the edges, the more the sheath will be damaged. Climbing on fractured rock, quartzite sandstone or sharp granite can accelerate this process. Frequent rappelling and top-roping can also accelerate ageing far more than climbing a rope without loading it.