Re-purposed suitcase cold frame

Has anyone seen this use for old suitcases?  I saw it on the Backyard Diva facebook page.  How many old suitcases have you passed up for $1 at yard sales?  This didn't have instructions with the picture but I found the directions online at this site _ http://www.flickr.com/photos/tomandemma/sets/72157622462783382/with/3957266675/