It may be fastened with buttons, a zip, velcro, or snap fasteners. Recently many manufacturers use bolt on fasteners. This recess is optimized to fit on the threaded end of aerospace fasteners. All other cars were modified by replacing the adhesive with mechanical fasteners. Stapleless staplers cut and bend paper without using metal fasteners. Titanium, aluminum, and various alloys are also common materials of construction for metal fasteners. The structural components are, generally, the frame members, bearings, splines, springs, seals, fasteners and covers. These joints are usually glued and can be reinforced with mechanical fasteners. In 1898, the standard for metric threaded fasteners was established. Building materials for hanging include ropes, wire cables, tension fasteners, and springs. The two-flap closure is secured by means of metal snap fasteners. Tapered threads are used on fasteners and pipe. During mealtimes astronauts use trays that attach to their thighs using springs and fasteners. The loops use hook and pile fasteners and snaps. Velcro is a privately held company that produces fasteners and other products.