with further reference to the drawings , the chair of the present invention is shown therein and indicated generally by the numeral 10 . chair 10 includes a base frame indicated generally by the numeral 12 . base frame 12 comprises opposed side frames and certain interconnecting support structures . in particular , each side frame includes a vertical member 13 , a base members 14 , a diagonal or front brace 16 , and a side rail 18 . in addition , extending across the front of the chair between the side rails 18 is front cross member 20 . spaced behind the front cross member 20 is a back cross member 22 . in addition , a lower cross member 24 extends between the base members 14 of the side frame . disposed on the base frame 12 is a seat 28 . although not required , the base frame is supported by a series of wheels 26 . disposed below the seat 28 is a catch 30 that is in the form of a rail . as seen in the drawings , catch 30 extends between the vertical members 13 of the side frame and is supported at a height generally intermediately between the top and bottom portions of the base frame 12 . catch 30 includes a top surface 30a and a rear side 30b . note that in the embodiment illustrated herein , the top surface 30a angles upwardly from the front of the catch 30 toward the rear side 30b . spaced above catch 30 is a retainer 40 with a back side 40a . retainer 40 is also in the form of a rail and extends transversely across the back of the base frame just rearwardly of the back cross member 22 . a space is defined between the back cross member 22 and the retainer 40 . that space , as will be discussed subsequently herein , enables the back of the chair to be inserted therethrough . also , there is a throughway defined between catch 30 and retainer 40 and as will be appreciated , the back can move through this throughway . now , turning to the back of the chair 10 , the back is shown in the drawings and indicated generally by the numeral 60 . as will be appreciated , back 60 is movably mounted within the throughway defined between the catch 30 and the retainer 40 . in the case of the design illustrated herein , back 60 includes a pair of laterally spaced vertical support members 62 . each support member 62 includes a lower portion . formed on the lower portion of each vertical support member 62 is a notch that is designed to engage the catch 30 . in particular , each notch includes a side surface 62a and a top surface 62b . note that side surface 62a is open towards the front while the top surface 62b angles downwardly toward the front of the respective support member 62 . as appreciated from the drawings , the respective notches formed on the lower ends of the vertical support members 62 are designed to mate with the catch 30 and particularly designed to mate about the top surface 30a and rear side 30b . in addition , formed about the lower portion of each vertical support member 62 is a stop 62c . this stop 62c is formed on the back of the support member 62 opposite the respective notches . as seen in the drawings , the respective stops 62c project rearwardly . the purpose of the stop 62c is to prevent the back structure from being pulled entirely out from the space defined between the back cross member 22 and retainer 40 . that is , it is appreciated that if the back 60 is continued to be pulled upwardly , the stop 62c will engage the lower portion of the retainer 40 and prevent the support members 62 from being pulled from the base frame 12 of the chair . the back 60 also includes a cross member 64 that extends between the lower portion of the support members 62 . it is appreciated that various cross members and other reinforcing structure can be incorporated as needed in the base frame as well as the back . back 60 also includes a back pad 66 . the back pad 66 extends transversely and is effective in the present design to form a stop when the back 60 is moved downwardly to its retracted or stowed position . in particular , as seen in fig3 when the back 60 assumes the downward retracted or stowed position , the pad 66 effectively contacts and stops against the side rails 18 that in the present design form a part of the respective side frames of the base frame 12 . in the upper operative position , it is seen that the support members 62 of the back 60 extend through the throughway defined generally between the catch 30 , retainer 40 and back cross member 22 . note that the notches formed in the lower portion of the support members 62 engage the upper and back portion of the catch 30 . in particular , the top surface 62b of the notch rests on the angled upper surface 30a of the catch . this basically supports the back 60 vertically and prevents the back from moving or falling downward . at the same time , the rear side surface 62a engages the back or rear side 30b of the catch . this prevents the lower portion of the support members 62 from rotating counterclockwise as viewed in the drawings . the back 60 in the upper operative position is further stabilized by the cooperative efforts of the retainer 40 . note that retainer 40 engages a back portion of the vertical support members 62 and prevent the adjacent portion of the back structure from rotating counterclockwise as viewed in the drawings . thus , catch 30 in cooperation with the retainer 40 stabilizes the entire back 60 especially when back pressure is applied to the back by a person occupying seat 28 . now , to move the back 60 from the upper operative position shown in fig2 to the lower retracted or stowed position , the back 60 is simply lifted until the top surface 62b of the notches clears the top surface 30a of the catch . once this clearance is reached , the entire back 60 can be rotated towards the seat 28 and once the lower portion of the vertical support members 62 are aligned to pass rearwardly of the catch 30 , back 60 can be released and effectively lowered to the retracted or stowed position of fig3 . note again that there is a stop structure that limits the downward movement of the back 60 . in the case of the present design , the back structure and particularly the pad 66 is designed to engage the base frame of chair 10 to create this stop . it is appreciated that other types of stops may be employed for this same purpose . to raise the back 60 from the retracted or stowed position of fig3 to the upper operative position of fig2 the back 60 is simply lifted until the top surface 62b of the notches clear the height of the catch 30 . next , the back is rotated away from the seat or counterclockwise as viewed in the drawings . then the back is lowered to where the notches engage the upper and rear portions of the catch 30 . in fig4 there is shown another design for the chair 10 of the present invention . this design operates in the same manner as the chair disclosed in fig1 - 3 and described above . however , there are some differences insofar as the location of certain components of the chair . note in the design of fig4 where the catch 30 extends between the vertical members 13 of the side frame . also , it is appreciated that the respective side frames that form the base frame 12 of the chair is of a slightly different design . in the chair disclosed in fig4 the opening between the vertical members 13 and the forward structure of the base frame 12 extends upwardly to a point adjacent the upper portions of the base frame 12 . but again , as noted above , the basic structure and operation of the chair 10 remains the same . the present invention may , of course , be carried out in other specific ways than those herein set forth without parting from the spirit and essential characteristics of the invention . the present embodiments are , therefore , to be considered in all respects as illustrative and not restrictive , and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein .