An apparatus, comprising: a shackle comprising: a body portion; a first leg extending from the body portion and including a first foot (116; 216; 316; 416; 516; 616; 716; 816; 916); and a second leg extending from the body portion and including a second foot (116; 216; 316; 416; 516; 616; 716; 816; 916); wherein each foot (116; 216; 316; 416; 516; 616; 716; 816; 916) comprises: a tip portion (150; 250; 350; 450; 550; 650; 750; 850; 950) having a non-circular outer cross-section; and a groove (118; 218; 318; 418; 518; 618; 718; 818; 918); the apparatus further comprising: a tubular housing extending in a longitudinal direction and including: an internal cavity; a pair of first openings offset from one another in the longitudinal direction and sized and configured to receive the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916); and a lock mechanism including a pair of deadbolts positioned in the housing, the lock mechanism having a locked state in which each deadbolt is engaged with the groove (118; 218; 318; 418; 518; 618; 718; 818; 918) of a corresponding one of the feet (116; 216; 316; 416; 516; 616; 716; 816; 916) and retains the corresponding foot (116; 216; 316; 416; 516; 616; 716; 816; 916) within the housing, and an unlocked state in which the deadbolts do not prevent removal of the feet (116; 216; 316; 416; 516; 616; 716; 816; 916) from the housing, characterized in that the tubular housing further comprises: a pair of second openings offset from one another in the longitudinal direction and sized and configured to receive the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950) of the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916), each of the second openings having a non-circular inner cross section corresponding to the non-circular outer cross section of the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950); wherein the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916) extend through the pair of first openings such that the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950) are received in the second openings. a shackle comprising: a body portion; a first leg extending from the body portion and including a first foot (116; 216; 316; 416; 516; 616; 716; 816; 916); and a second leg extending from the body portion and including a second foot (116; 216; 316; 416; 516; 616; 716; 816; 916); wherein each foot (116; 216; 316; 416; 516; 616; 716; 816; 916) comprises: a tip portion (150; 250; 350; 450; 550; 650; 750; 850; 950) having a non-circular outer cross-section; and a groove (118; 218; 318; 418; 518; 618; 718; 818; 918); a body portion; a first leg extending from the body portion and including a first foot (116; 216; 316; 416; 516; 616; 716; 816; 916); and a second leg extending from the body portion and including a second foot (116; 216; 316; 416; 516; 616; 716; 816; 916); wherein each foot (116; 216; 316; 416; 516; 616; 716; 816; 916) comprises: a tip portion (150; 250; 350; 450; 550; 650; 750; 850; 950) having a non-circular outer cross-section; and a groove (118; 218; 318; 418; 518; 618; 718; 818; 918); a tip portion (150; 250; 350; 450; 550; 650; 750; 850; 950) having a non-circular outer cross-section; and a groove (118; 218; 318; 418; 518; 618; 718; 818; 918); a tubular housing extending in a longitudinal direction and including: an internal cavity; a pair of first openings offset from one another in the longitudinal direction and sized and configured to receive the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916); and an internal cavity; a pair of first openings offset from one another in the longitudinal direction and sized and configured to receive the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916); and a lock mechanism including a pair of deadbolts positioned in the housing, the lock mechanism having a locked state in which each deadbolt is engaged with the groove (118; 218; 318; 418; 518; 618; 718; 818; 918) of a corresponding one of the feet (116; 216; 316; 416; 516; 616; 716; 816; 916) and retains the corresponding foot (116; 216; 316; 416; 516; 616; 716; 816; 916) within the housing, and an unlocked state in which the deadbolts do not prevent removal of the feet (116; 216; 316; 416; 516; 616; 716; 816; 916) from the housing, a pair of second openings offset from one another in the longitudinal direction and sized and configured to receive the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950) of the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916), each of the second openings having a non-circular inner cross section corresponding to the non-circular outer cross section of the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950); wherein the first and second feet (116; 216; 316; 416; 516; 616; 716; 816; 916) extend through the pair of first openings such that the tip portions (150; 250; 350; 450; 550; 650; 750; 850; 950) are received in the second openings.