The arms, being chrome plated, are so smooth that to fix the telescopic arm so that it does not slide back in requires considerable force to be applied to the gripping key. The gripping key is tightened using a chrome plates knob. The outside edge of chrome this knob is so smooth that it cannot be tightened sufficiently to fix the telescopic arm. The knob should have a knurled edge to enable it to be easily gripped.