formed of spaced u shaped end members 12 end members 12 are connected by longitudinal cross members 15 which extend the length of the assembly each end member 12 includes vertical legs 13 between which a support 16 extends guide channels 20 and 22 as shown in fig3 5 are carried upon each support 16 the connecting linkage extending from each end member 16 is the same and thus only one complete end member is shown and will be described it is understood that the other end member 16 and connecting linkage specifically described works and is constructed in similar fashion a link 24 is pivotally connected at 26 to front leg 13 of u shaped member 12 and is connected to the front of a seat support 28 at pivot 30 a bench type seat cushion 76 is attached to support 28 a link 32 is slidably retained at its lower end 34 for movement along guide channel 20 by a roller not shown located within the guide channel and is fixedly connected at its upper end 36 to the rear of seat support 28 a link 38 is pivotally connected at one end 40 to seat support 28 adjacent link 32 and is slidably retained for movement along guide.