The vertical blocks are used to terminate the permanent outside lines entering the station.
This arrangement permits the association of any outside line with any desired terminal equipment.
These connections are made either with twisted pair wire, normally referred to as jumper wire, or with optical fiber cables, normally referred to as jumper cables.
In technical control facilities, the vertical side may be used to terminate equipment as well as outside lines.
This article incorporates public domain material from Federal Standard 1037C.