Mercury - J-Box Stacking Plug Kit Vertical SmartCraft Alignment 23-8M0174363. Overview. SmartCraft networks can get messy when the boxes are scattered or mounted at odd angles. The Mercury 23-8M0174363 J-Box Stacking Plug Kit helps clean things up by letting you stack multiple J-boxes vertically so all the plugs line up on one side. It gives the rigging a more organized look and makes it easier to reach the ports without fighting cramped spaces or tangled wiring. It's a small piece, but it makes