The holes are spaced in a repeating pattern every 0.625 inches (15.875 mm) across the vertical height. Three holes per U:
Understanding the EIA-310-D Standard for Server Racks and Enclosures
The Electronic Industries Alliance (EIA) was a prestigious trade organization that developed consensus standards for electronics manufacturing. The "310" series specifically addresses . The "D" revision marks a specific, mature iteration of this standard. eia310d standard pdf
Minimum 17.75 inches (450.8 mm) . This is the internal space between the front vertical rails. The chassis of the server or equipment must be narrower than this dimension to slide into the rack. Vertical Dimensions: The Rack Unit (U)
The EIA-310-D standard is the bedrock of modern data center infrastructure. Published by the Electronic Industries Alliance (EIA) in 1992, this specification defines the critical dimensions for 19-inch racks, cabinets, panels, and associated equipment. The holes are spaced in a repeating pattern every 0
The Definitive Guide to the EIA-310-D Standard for Server Racks
The standard governs the spacing of the holes, but not their shape. Modern racks employ three different types of holes on their vertical mounting posts: The "D" revision marks a specific, mature iteration
The "19-inch rack" name refers to the width of the equipment's front panel, not the opening of the rack itself. The standard breaks down horizontal dimensions as follows: 19.0 inches (482.6 mm)