In industrial and commercial applications, mezzanine floors are semi-permanent floor systems, built between two permanent original stories or built to make use of unused high level space. Mezzanine floor structures are usually free standing and can normally be dismantled and relocated. Commercially available mezzanine structures are generally constructed of three main materials; steel, aluminum, and fiberglass. The decking or flooring will vary by application but is usually of wood or wood product or a heavy duty metal grating. Mezzanines are often used for storage. They should therefore be designed to withstand all likely loads and the safe loading capacity and details of any restrictions should be clearly and conspicuously marked. Suitable means of access must be provided and edge protection should be provided on every open side. If a fork lift or reach truck is used for loading and unloading goods a pivoting safety barrier (pallet gate), which provides continuous edge protection for all employees not just those engaged in the loading activity should be used. The support structure for every mezzanine floor must be routinely inspected for damage and to ensure its continuing integrity.