There has been discussion on the FML about sleep boxes and the advantage it has to keeping sleep places dark. I have used sleep boxes in all my cages at the shelter almost from the inception of the shelter. Below is the description of the boxes I use and sell in my store, with a link to the picture; compliments of Harry Pike so you can see what the fur kids do to keep it dark and warm. Brenda Small sleep box: Made of Balsa plywood sanded to a soft finish, topped with permanent vinyl flooring for durability and easy cleaning. The sleep box is 8 1/4" X 10" X 8" with a 4" opening for entry. This sleep box belongs to Evita and Junior, two fur kids left of a 3 group. Notice the blanket in the box. I put receiving blankets or sleep sacks in all the sleep boxes in all the cages. The fur kids get in and stuff the blanket or sack in front of the hole so it is all cozy and dark in there. This box held all 3 kids with no problem, it can hold up to 4 ferrets at one time. Ferret tested and approved by our shelter ferrets. Bradley's Sleep Box (large) Made of Balsa plywood sanded to a soft finish, topped with permanent vinyl flooring for durability and easy cleaning. The sleep box is 10 1/4" X 11" X 7 1/2" with a 4" opening for entry. This sleep box belongs to Des and Ophelia. Notice the blanket in the box. I put receiving blankets or sleep sacks in all the sleep boxes in all the cages. The fur kids get in and stuff the blanket or sack in front of the hole so it is all cozy and dark in there. This box will hold up to 5 kids with no problem. Ferret tested and approved by our shelter ferrets. Link to webpage for sleep boxes <http://www.kwflatbed.com/brenda/sleepboxes.html> [Posted in FML issue 5241]