Toolies Piston Valve
A toolies piston valve is a type of inline barrel-sealing piston valve which allows inline (or any) configuration launcher setup with more effective chamber volume than a simple coaxial barrel-sealing piston valve.
The toolie's type valve consists of an air chamber. At one end (the pilot end), a large piston sits which is the same diameter as the inside of the pipe. A long rod (threaded rod, smooth rod, pipe nipple, whatever) reaches all the way to the other side of the chamber, where it ends in a sealing face only marginally larger than the outside diameter of the barrel. This rod also usually has a spacer to center it in the air chamber.
When the pilot is exhausted, the piston will move back because of the force pushing against the other side of the larger piston, and against the small exposed area on the barrel-sealing piston. Like most barrel-sealers, there is a "jump" in force as the barrel-sealer unseats from the back of the barrel, and the piston moves backwards.