Manthorpe 4-Way SlotDrain Drain Channel Junction Black Pack of 6 Junctions Description The SlotDrain Junction Unit (GPDST-JU) is made up of 3 components; a channel base, an extension piece and a grate lid. In any run of SlotDrain, a Junction Unit should be used at each end to enable access for rodding and cleaning. In longer runs, a Junction Unit should also be placed at 3m intervals. Junction Units can also be used to create a 90 corner, a T-junction or a 4-way junction.