An elongate header for mounting a connector. The header includes a series of insulative L-shaped segments each including a base having an aperture for receiving a header post and further including a resilient, deflectable wall extending from the base. Adjacent segments are joined by interconnection means sufficiently thin that a group of segments can be broken away by hand from the remainder of the segments. The header also includes a post disposed in each aperture, the locking means for cooperating with a component of the connector to lock the connector, once mounted to the header. Finally, the header includes polarizing means for preventing reverse mounting of the connector on the header. Headers of a predetermined number of segments can be removed from an indeterminate length of such segments to preclude the need for a user to carry an inventory of headers of different lengths.