I'm a relatively new Gitzo 1542T owner. The 1542T is designed to be usable both with and without the centre post. I've practiced taking the centre post in and out a few times, and I'm not sure reassembling the tripod correctly. When I extend the centre post, it slides right back down. I can't seem to make it lock in place, even when I twist the twist-lock collar at the base of the centre post (it looks similar to the twist lock on the tripod legs). When I use the tube shaped thing on the centre column, I can make the centre column stay in place when it is extended. However, when I look at photos on the internet, it looks as the the centre column is meant to stay extended without using the tube shaped thing. For some reason the tripod did not come with diagrams or a manual, and as a result I can't be confident of my attempts at reassembling the tripod.