The Telecommunications Closet (TC) or Intermediate Distribution Facility (IDF) designed/sized to serve the floor on which it is located, and the floors above and below, based on the assessment results. This closet is to be centrally located so as to ensure that all copper voice and data cable sheath lengths out to the outlets are less than 90 m (295 ft). In larger buildings, several IDFs per floor may be required to adhere to this maximum cable length requirement. The overall design shall minimize the total number of closets while staying within the 90 m (295 ft) requirement. Closets shall be located such that vertical cable installations are limited to three floors either above or below.

This is where horizontal cabling starts, and it is where to local a patch panel or cross-connects.

There may be an unlimited number of closets containing the telecommunication equipment used for facilitating horizontal wiring connections. The layout can include several closets per floor, if necessary.