A rope is a linear set of plies, yarns or strands, twisted or braided together to combine them into a larger and stronger form. Ropes have tensile strength and can be used for dragging and lifting. Rope is important in construction, seafaring, exploration, sports, hangings, theatre, and communications. Rope has been used since ancient times. To fasten a rope, a large number of knots have been invented for countless uses. Common natural fibres for ropes are manila hemp, hemp, linen, cotton, coir, jute, straw and sisal. There are two types of ropes, rock climbing ropes and aerial ropes.