Abstract: An adjustable lock arrangement for rods, tubes, and the like, comprising a rigid collar having a central opening in which a rod segment is closely received. The interior surface of the collar includes a keyway in which an eccentric key is rotatably mounted. The key includes a first surface, which when rotated toward the rod, permits the collar and rod to slide telescopingly with respect to each other, and a second, outwardly protruding surface, which is rotated into abutting engagement with the rod to frictionally lock the collar and rod in place. The collar may be formed as a separate unit for use as a couple, an adjustor, et cetera, or integrally constructed with the end of a tube for interlocking telescoping segments of a support, or the like.