Bilateral crutches are infrequently used in older adults to eliminate weight bearing on one leg. Crutches are made of either aluminum or wood, and are adjustable in height at the base and hand piece. The top bar should be two inches below the armpit, and the hand pieces should allow a fifteen-degree angle at the elbow. Crutches require considerable balance, strength, and coordination (for proper sequencing of crutches and legs) to use safely, and have been associated with injury to the axillary artery. As crutches are often too difficult for older persons to use, walkers are generally preferred when weight bearing is only permitted on one leg.