Chair tray apparatus

A tray for a chair comprises tray 18, guide seat 2 disposed on chair arm 17 and a locking unit wherein the tray engages the guide seat and the guide seat has two parallel corrugated plates 21 forming a groove (20, fig. 2) which contains the locking unit. The locking unit comprises control member 3, with post 31, slidable in groove (20) and click box 4 disposed on control member 3 and in slide rail 181 of tray 18. Click box 4 has an oblong slot 41 into which post 31 is inserted and a distal positioning end 42 that engages a corrugated plate 21 to lock tray 18 into position. Tray 18 preferably has pillars 183 which engage oblong grooves 22 on guide seat 2. A coiled spring 5 is preferably located between sockets 32, 182 on control member 3 and tray 18.