I didn't contribute to this discussion earlier but Clare has now put up a very useful summary. While the focus was naturally on archive maps, I think Martin Taylor's point regarding Ordnance Survey maps was worth underlining. Our local studies collections in Manchester include ane xtensive range of OS maps which have been stored in horizontal map cabinets for many years. As a result, their condition has deteriorated markedly, as staff are inevitably tempted to try and pull out a map without removing those stored on top. We switched some maps to vertical file cabinets as an experiment several years ago, and these are clearly superior in terms of preservation, since it is much easier to access individual maps. We have had no problems with hangersb ecoming detached, though we were careful to use the (admittedly expensive)h angers supplied by the map cabinet company, which need no specialist equipment to attach. Our OS maps are very heavily used indeed, and where this is the case, I would argue that a vertical map cabinet is a more efficient use of floors pace, as stacking horizontal map cabinets more than about 1 metre high would simply not be practicable.

Incidentally, if any one has any experience of using digital copies of OS maps in place of the originals, I'd be interested to hear them. The Ordnance Survey can supply digital copies made by Landmark but these are hedged with all sorts of restrictions. Following Jonathan Pepler's mailbase message, we purchased from an alternative source, Sitescope; this was a much better deal but they still have not supplied the promised tweaks in the printing software. Does no one else have major problems with crumbling OS maps?