Modern strong fibers such as PBO ( IUPAC name: poly(p-phenylene-2,6-benzobisoxazole), aramids ( Kevlar , Technora , Twaron , Vectran , carbon fibers ), ultra-high-molecular-weight polyethylene ( UHMWPE )—or Dyneema and other synthetic fibers are used to make extra strong ropes which can also be tied into lockable loops called soft shackle .  According to "a soft shackle can handle just about every function performed by a metal shackle, in many cases better. Soft shackles articulate better, don’t rattle around when not under load, don’t chew up toe rails or beat up masts and decks, don’t hurt when they whack you on the head, are easier to undo and don’t have pins that fall overboard at a critical moment".  A modern rope can lift as heavy loads as a steel wire 3 times as thick and much heavier. When a soft shackle fails it is almost always at the diamond knot made of the strong slippery rope that sucks the tails in under heavy load.