Below is a list of Rack Mount Enclosures manufacturers from Frederick, Maryland. Rack mount enclosures have standardized frames and racks for mounting multiple electronic equipment modules. Vertically stacked equipment saves floor space and is easier to maintain. The enclosures and modules are 19 inches wide, and the height is measured in multiples of 1.75 inches, each called one rack unit (U). There are three vertical holes in every 1.25 inch along the post with half an inch between the set of three holes; this is where the equipment is mounted.