Chair backs adjust in a number of different ways. A popular method is the ratchet back which is very simple to set up. Built into the back support is a ratchet mechanism. To move it up you would normally grip the back on each side at its base and push it up gently. As you do so you will find the back clicks a little higher to a number of preset positions. So once you find the one that works for you that's it.And in case you need to start out again if you lift the back up to its maximum height it usually drops back down to the lowest position so you can start over if necessary.Sometimes there may be a couple of buttons to press in while you adjust the back. As soon as you reach the desired height just release them to lock in your preferred height.Some Office Chair Singapore use a locking knob. You would undo it to let you move the back and then tighten it again to save the height setting.So much for adjustable backs what if it's fixed?