Shelves are racks used to store or display objects. Shelves are needed in every home. Wood shelves in kitchens, bathrooms, attics and basements make good storage spaces. They look neat and save a lot of space. Shelves are sometimes adjustable and can be elongated to desired lengths. These shelves are usually mounted on extendable rods. Non adjustable shelves are usually used in closets, attics, basements and work areas. These shelves are usually nailed together with support pieces in order to provide desired structural strength. The strength of the shelves depends on the way in which nails are driven into the walls. Nails driven at outward angles are most likely to pull out when heavy loads are placed on them. If the nails are driven straight inside, the supporting strength of the shelf increases. The heaviest loads can be taken by nails driven downwards.