An extendable channel unit such as molding unit (21) has a pair of telescopically arranged relatively extendable conduits (55, 75) with a conductor (22) interconnected in conductive relation between the conduits, with an intermediate section (137) of the conductor effective to accommodate the relative extension of the conduits. The intermediate section may include a sinuous configuration (133) or expandable coils (139). The channel unit may be installed along a wall (145) or other surface for decoratively covering the installation of the conductor for connection with an operated device (153). The channel unit may be installed into an extendable ramp (163) when installed along a floor, such as within a doorway (171). Two joints (308, 310) provide freedom of rotation about the conductor axis on opposed sides of an angled joint (312) that provides freedom of rotation about an axis disposed at a 45.degree. angle to the axis of the conductor. This combination permits the unit to be configured to pass around both inside and outside corners, as well as to form upward and downward right angles along a straight wall.