on a shaft 112 which is fixedly attached to and extends orthogonally inwardly from side rail 32 of midframe 12 it can be seen that wingframe 14 is freely rotatable from its folded position fig6 and 7 to its outwardly extended position fig2 but that once the wingframe reaches its outwardly extended position it is prevented from further such rotation by and is supported in part by the engagement of flattened portion 110 with the top of end rail 34 of midframe 12 a similar structural arrangement not shown on fig5 provides for the support of side rail 46 similarly the proximal end of vertical rail 62 of leg member 18 terminates in a flattened portion 120 see also fig1 and 2 which is rotatably disposed on shaft 112 and which flattened portion includes an integral flange 122 extending outwardly therefrom vertical rail 62 is freely rotatable from its folded position fig6 and 7 relative to midframe 12 until it reaches the position shown on fig2 at which time further rotation is prevented by the engagement of flange 122 with the underside of end rail 34 of the midframe a similar structural arrangement causes stopping engagement of vertical rail 60 with end rail 32 thus with leg member 20 similarly stoppingly engaged with midframe 12 rack 10 may be placed in and.