aluminum and have a sufficiently heavy wall to provide a sturdy support able when extended to resist the force exerted by the ladder 10 and if any tendency to tip sideways occurs the inner tube 22 has a flattened tip 25 which has a hole 23 formed therein sized to receive the cross tube 18 a pair of retainer end caps 19 are installed to keep the same on a respective tube end the lower end of each outer tube 24 has a nonskid tip 27 installed thereon a one way acting brake 26 is installed on the upper end of the outer tube 24 which allows the inner tube 22 to freely telescope out of the outer tube 24 as the outer tube 24 drops away under the influence of gravity but instantly engages to rigidly connect together the tubes 24 26 to resist any telescoping together of these tubes 22 24 if a pushing force is exerted on the upper tube 22 after the outer tube 24 contacts the supporting surface each one way acting brake 26 comprises an annular disc 28 preferably of steel which is held at an inclined angle on the upper end of the outer tube by an upwardly and outwardly angled reaction tab 30 formed in a metal strip 32 affixed as by welding or by other means to one side of the upper end of the outer tube 24 the reaction tab 30 contacts the bottom surface of the left.