manner similar to the working example of fig6 in the case of such an embodiment as in fig9 it is possible to provide for additional latching at the other end of the bail 4 or respectively chair member 1 as is depicted in fig1 moreover it is in accordance with the embodiment of fig1 possible for the retaining part 4 or respectively the bail 4 to be further divided up that is to say using a further rotary joint 18 it is in this manner that it is possible for a coarse and fine latching or respectively positioning of the bail 4 to be achieved more especially when the rotary joint 18 also has integrated latching function which renders possible a plurality of latching positions as is the case with the preceding embodiments in this case then the bail 4 may be firstly coarsely set by way of the rotary joint 15 and the latching means 16 integrated in it while by pivoting the bail 4 about the rotary joint 18 with the integrated latching means 39 fine setting of the position is possible in the case of this embodiment the pivot point 15 can be arranged centrally in contradistinction to the preceding embodiments a still further embodiment of the retaining system is illustrated in fig1 a and 12 b in the perspective view of fig1 a it will be seen that the retaining device is also divided up into a linkage 17 and a retaining bail 4 the linkage 17 being arranged for rotary movement about the rotary joint 15 whereas the retaining bail 4 is again attached to the linkage 17 by way of rotary joint 18 the linkage 17 is able to be freely turned about the rotary joint.