assembly 14 support assembly 16 can then be inserted into the bottom end of lower cylinder 30 of upright assembly 14 as shown in fig5 7 the length of retention pin 94 is short enough to allow for its insertion into upright assembly 14 while at the same time retention pin 94 guides support assembly 16 into the lower end of lower cylinder 30 to avoid contact between clamping bar 92 and any burrs or the like that may be present within the internal diameter of lower cylinder 30 a retention lever 122 is pivotally secured within lower cylinder 30 of upright assembly 14 to retain support assembly 16 within lower cylinder 30 a biasing spring 124 biases lever 122 against support assembly 16 for retention base locking screw 20 is loosened to disengage screw 20 from lower cylinder 30 of upright assembly 14 this allows for the approximately 270 u00b0 rotation of base 18 from the open position shown in fig1 3 to the collapsed position shown in fig5 7 base legs 22 are pivoted from their open position as shown in fig1 3 to their collapsed position as shown in fig5 7 height adjustment pin 34 is removed from lower cylinder 30 and outer sliding cylinder 32 outer sliding cylinder is slid and rotated from its open position as shown in fig1 3 to its collapsed position as shown in fig5 7 in this collapsed position locating stud 46 engages locating slot 54 causing the alignment of apertures 52 and 44 height adjustment pin 34 is inserted into apertures 52 and 44 to retain upright.