SummaryThis tube endcap is made for telescopic tubes. The endcap needs a cut ring of vinyl tube placed in the "low area" to function. When assembled correctly, giving a twist to the interior tube of a telescopic tube set, will lock the tubes or unlock the tubes... adjusting the length. A similar function to this can be found in adjustable shower curtains.InstructionsThis tube endcap is made for telescopic tubes. The endcap needs a cut ring of vinyl tube placed in the "low area" to function. When assembled correctly, giving a twist to the interior tube of a telescopic tube set, will lock the tubes or unlock the tubes... adjusting the length. A similar function to this can be found in adjustable shower curtains.