Minecraft wiki entry for Furniture, associated text: Placing stairs upside down allows functional stair shelves. Blocks are split into two halves (thus two slabs of the same material make 1 block) so point your cursor at the TOP HALF of the block you want your shelf against and place your stair; if you aim lower it will be right-side-up and you have to replace it. If you aimed for the top half of the placement block it will become upside-down and you can make non-floating cake holders. This way you can skip the trouble of placing a block and your stair and removing the reference block. Place them outside under a window for a windowsill, or maybe even use several with crafting tables mixed in for a cat tree.