Perhaps I should not mention my own work here, but in the book "Rock garden design and construction," which I edited for Timber Press/NARGS, there is a chapter on bulb and alpine frames, with good line drawings by Suky McDonough (our correspondent Mark's wife), and photos of the extensive bulb frames where I used to grow my collection. In the photo book "Bulbs" by Martyn Rix and Roger Phillips, there is a photo in the introduction of a bulb frame under construction; it is apparently designed to grow the bulbs in the fill soil, not in pots. To the descriptions already posted, I would add that it is strongly advisable to include some kind of barrier at the bottom of the frame. I use industrial-strength woven groundcloth, which for many years has deterred moles from digging in from below -- and where moles pioneer a tunnel, mice and voles are sure to follow. I used this same product to line the raised beds where my bulbs are now growing, as well as the path between the beds, which is paved with crushed rock. The beds are under a polycarb roof in a commercial steel-frame greenhouse with metal mesh walls. Although most cold frames are of the "shed" design, with hinges on one side, I think it's far better to have an "A-frame" design that opens on both sides for access and ventilation. However, building an A-frame takes more carpentry skills than I have (i.e., more than none), so I paid someone else to build mine. In the UK gardeners can buy "Access" frames that are made like miniature greenhouses with opening panels on the sides, but I've heard anecdotally that these don't stand up well to heavy snow loads or strong winds. Jane McGary Portland, Oregon, USA