When I did this last year, I took lots and lots (and I mean lots!!) of photos particularly of the cross struts and boltings, from all sorts of angles. I then labelled each metal piece as I took it off using a permanent marker, I also labelled each piece of glass that I was keeping. There were several months between taking it down and putting it back up on a new concrete base with a breeze block edging, at which time I found out that "permanent" didn't quite mean that!! However, the photos saved the day. I am now the owner of a free 6'x6' GH. The glass size was a standard 2'x2' horticultural glass, just a few pounds each, (£4?). Luckily I only needed two! Good luck