Usually hand made from a foam core (or "blank") with a wooden stringer that is sanded to the desired shape then coated with clear fiberglass/resin. Modern boards have anywhere from one to five fins arranged at the tail end of the board. Fins vary in size, stiffness, and shape and can often be changed to suit the rider or conditions. Boards can also be made from epoxy, carbon fiber, and multi-layered foam. An elastic leash is usually attached to the rear to make retrieving the board easier. While a surfboard can withstand hundreds of pounds of force they are also fragile and break down when left in hot areas (such as cars) and direct sunlight.