A trundle bed is one that will slide underneath another bed in your home. Trundle beds are great for guests and make a perfect addition to a child’s room, providing a great spot for friends to sleep over. Because the trundle slides under another bed, there is no reason why the trundle needs to be an ornate and fancy piece of furniture. A simple trundle bed with a foam mattress can slide underneath and be ready for any guest. In this case, you can also use it as a place for your dog to sleep.