An elongated device such as a multisectional rod constructed of a plurality of elongated component elements arranged end-to-end when the rod is in its extended configuration. A flexible, releasable tension member secures the component elements in endto-end contact and, upon release of the tension member, permits the elements to be collapsed. At least one core is disposed within each of the component elements. The cores have oppositely, longitudinally spaced front faces and they are longitudinally shiftable relative to the component elements. When the tension member is tightened, the respective core faces contact one another and the cores are shifted relative to the component elements into a position in which their front faces are axially offset relative to the ends of the component elements to thereby rigidly interlock the component elements in their extended, endto-end contact and to thereby form a rigid, elongated, straight rod.