Abstract: A T-joint having a two-part housing applicable to a pipe contains a member adapted to cut a hole in the pipe when acted upon by an explosive charge to provide a branch conduit from the pipe. The explosive charge is contained in a nut attachable to the housing and is ignited by a percussion cap. The bottom portion of the nut is provided with three concentric recesses, each one smaller than the preceding one. The first recess holds the charge, the second recess holds a breech member for the percussion cap, and the third recess holds an anvil for firing the cap.