to foot body 22 fig5 is a bottom view of foot 20 as may be observed in fig4 and 5 foot bore 24 comprises a plurality of foot bore notches 34 communicating with foot bore 24 back 10 comprises back shafts 12 rigidly attached to back support 13 back shaft notch 14 is disposed at an extreme of back shaft 12 opposite back support 13 back shaft notch 14 divides an extreme of back shaft 12 opposite back support 13 into back shaft key lobe 15 and back shaft lip lobe 17 back shaft key 18 is disposed on back shaft key lobe 15 and back shaft lip 16 is disposed on back shaft lip lobe 17 back shaft key 18 is sized to fit into foot bore notches 34 thereby holding foot 20 at a pre determined angle relative to back 10 either in the unfolded configuration as depicted in fig1 and 2 or in the folded configuration as depicted in fig1 and 15 back shaft lip 16 is sized to exceed the diameter of foot bore 24 thereby serving to retain back shaft 12 within foot bore 24 as depicted in fig4 foot body cap 36 frictionally fits over an extreme of foot body 22 opposite back support.