A printer ink supply system that includes a docking station having a pair of separated keying members and another docking station having another pair of separated keying members, wherein the docking station and the other docking station can be arranged in a stacked relationship when one of the keying members on the docking station is interlocked with a keying member on the other docking station. The keying members are distributed on the top, bottom and side walls of both docking stations thereby enabling the two to be interlocked in top to bottom or side to side relationships. The docking stations are interchangeable and any number can be joined in vertical or horizontal relationships, or in combinations of vertical and horizontal relationships.