Abstract: A method and apparatus for assembling a spool valve into a valve bore of a body by providing compressed gas to the valve bore at a pressure below the pressure of compressed gas supplied to a passage within a carrier body containing a spool valve substantially concentrically aligned with the valve bore to advance the spool valve from the passage into the valve bore. The compressed gas in the passage provides a force acting generally uniformly on the spool valve substantially concentrically aligning the spool valve within the passage. The compressed gas supplied to the valve bore also acts substantially uniformly on the spool valve tending to substantially concentrically align the spool valve within the valve bore when the spool valve is advanced therein. While the gas in the passage and the valve bore align the spool valve, the higher pressure of the gas in the passage advances the spool valve into the valve bore.