Arm rest on middle seat bench

I an having a problem with the arm rest on my middle seat. It either stays up or down along the back rest but never in the position to be used as a arm rest. How can I remove it and fix it. Thanks for the help.

One of GM's better ideas - there's a spot weld on the post that puts it into proper position. I had 3 fail on my 2002. I went to my local weld shop and paid the guy to properly well all of them in place.

The other problem is the POS plastic piece that mounts on the steel post - they go bad also. A $0.50 piece of plastic and you have to buy the whole armrest - another general great idea.