My collection of mounted prints is starting to grow, and storage is now becoming an issue. I currently store the prints either in a (really ugly) green portfolio (don't ask), or just stacked in my darkroom storage area. I would like to ditch the green monstrosity, and get something a bit nicer, like a portfolio box. However, trying to find a good portfolio box where I live is difficult at best - I've had no success finding boxes locally to store prints mounted on 16x20 and larger mount board. So, I've decided that I'll make my own. I've read up on the techniques, and constructing proper portfolio boxes, while time consuming, does not appear to be all that difficult. However, I'm not sure what materials to use for the box itself. In the books I've been reading, it appears that they *might* use something like mat board, but when you consider the bulk and weight of 15-20 photographs mounted on 16x20 mat board, I don't think mat board is up to the challenge. There's book board, or binder board, which is heavier and stronger than mat board, but I'm not sure how easy it is to work, never having held any in my hands. What other materials are there for this sort of project? Does anyone have any experience constructing these types of boxes? What materials did you use? Where did you get them? BTW, I know that you can purchase these boxes from various suppliers in the US (haven't found any in Canada yet), but at $75 a box (or thereabouts) plus the very expensive shipping, that's not really an option. I look forward to your comments.