Help with chair back

[holymonk]

I have never quite understood how to make an office chair back stay up. EG pulling up the back of the chair I hear a ratcheting sound but it always falls back down. I have tried all the levers and nothing seems to work. Also does anyone know what the grippy cylinder things on the bottom of the chair actually does (the one you twist clockwise/anti)?

 

[holymonk]

I worked it out, I meant specfically the chair back, I always lifted it to the top which was probably the mistake, lift it gradually and it stays up. thx anyway.