Abstract: A hollow through-bolt is threaded internally and externally, at one end, to receive therein a reciprocable, end-threaded rod. A pair of fluid-control valves, centrally bored, are mounted on the through-bolt in spaced apart disposition. The other end of the through-bolt has a shoulder formed thereon for seating one of the valves thereagainst, and the other valve central bore is tapped for threaded engagement with the one end of the through-bolt. A sleeve, slidably engaged with the through-bolt, and interposed between the valves, maintains the one valve positioned against the shoulder.