Formwork are temporary or permanent concrete forms for building structures from concrete. Basic specifications for concrete forms include height, width, and hole pattern. Face sheet, bracing, side rail, bushings, and welding are also important parameters to consider. Accessories for concrete forms include hardware such as brackets, braces, pins, wedges and wall ties. Related products include concrete form baskets, concrete form trucks, pouring accessories, release agents, and sealants that prevent the ingress of water. For lay-own applications, wire base ties and flathead pins are sometimes used. Face sheets for formwork are made from aluminum or other lightweight but durable alloys. They vary in terms of standard thickness, but are often commonly in .115 and .125. With some metal face sheets, welds are made near the edges to increase weld penetration, panel life, and panel strength. Gussets may be added for corner reinforcement. Side rail construction and bushing style are also important to consider. To extend the life of the face panel, side rails are often made of heavy-duty, extruded aluminum. Dual-contact designs help with proper alignment, and notches in the face sheet are used to strengthen the panel. Bushings for concrete forms are heat-treated, plated, and held in place with steel rivets. The rivets remain flush with the side rail to reduce the accumulation of concrete and make cleaning easier. Crowned bushings permit the release of wedges, and do not weaken the side rail like other bushings. Bracing construction is an important consideration when specifying formwork. To avoid weight gain from the accumulation of concrete, the hat section of the brace should be enclosed. Most concrete forms use metal tubes as braces. The tops and ends of these tubes are welded to strengthen the form and prevent the ingress of concrete. Extruded braces that feature a serrated design are easier to handle and help prevent slipping. For applications which require superior durability, double bracing may be used. Formwork whose braces use double tubes are suitable for light commercial applications, and provide a larger area for nailing.