Abstract: An improved circuit modification method is provided for wire-wrapped electrical back planes such that changes in the back plane circuitry may be accomplished in areas remote from a production facility where wire-wrap equipment and highly skilled technicians may not be available, such method involving the preparation of a slip-on, post-terminal-compatible printed circuit board at the production facility, delivery of the printed circuit board to the remote area, and the slip-on attachment of the printed circuit board onto the post terminals of the back plane by a repairman who may be unfamiliar with the intricacies of the back plane and its wire-wrapped interconnections, said slip-on printed circuit board being inherently provided with whatever guidance may be required by the repairman in effectuating its installation on the back plane.