I have used manual mobile shelving many times. You should ensure that the floor beneath the cabinets can hold the weight load, as you will be putting more weight per sq. ft. then normal. Usually your building folks have the plans. As usual ensure you have adequate space between the rows cabinets, usually 36" plus. Your height will depend upon your needs, but ensure that you meet the fire regulations with regards to height between the top of the cabinets and the ceiling. Most of the new cabinets move quite easily, but they can be somewhat heavy when they are full. Some of the mobile shelving I used created a safety issue, when two cabinets came together. There was a concern that they could crush a finger or foot. This was easily handled by putting rubber stoppers on the sides of the cabinets. The cabinets have tracks or bases which require a level surface. Most of the new ones do have levellers on them, but as much as possible ensure they are on a level surface. I had most of mine on a carpeted floor which didn't cause concern, but they do leave a mark on the carpet if you have to move them. This brings up another issue and that is modular shelving. I liked the kind of cabinets where you could add to them. In other words you could add another tier or remove a tier. I had my cabinets 7 and 8 tiers high and this wasn't a problem. You just have to ensure that they are levelled proportionately with anti tipping devices which I would insist they come with as standard. Also ensure they are coated with fireproof (baked enamel) paint and have a high rating (with the doors on) for heat and fire. The bases of these can get quite dusty as they are covered by the cabinet in front of them, so you should get the cleaner to dust often. The wheels should be self lubricated. Also get a good warranty on them and a maintenance plan. Just a few comments. Cheers. John A. Gervais Manager, Policy and Communications, Information Management Directorate, Finance and Administration Branch, Canada Customs and Revenue Agency, 16th Floor, Albion Tower, 25 Nicolas Street, Ottawa, Ontario, Canada, K1A 0L5 ' (613) 957-6621 * [log in to unmask] " http://www.ccra-adrc.gc.ca