Abstract: There is disclosed an extendible, locking tube assembly of outer and inner telescoping tubes. The outer tube internally carries a locking collar having an obliquely inclined central aperture that slidably receives an elongated locking member. An end of the elongated member is removably attached to the inboard end of the inner tube. The locking collar has a radial lug that projects exteriorly of the outer tube and bears against an abutment carried on the outside of the outer tube. The locking collar is biased into a position preventing retraction of the elongated member and its dependent inner tube. A lever, attached to the collar, projects exteriorly of the outer tube on the side opposite the abutment, thereby permitting a single-handed release of the locking mechanism. When the assembly is employed, as in its preferred application, with a carpet stretcher, one can release the locking mechanism without shifting one's position from that taken for operation of the carpet stretcher.