In the 091030 MMD Bruce Grimes writes:

    "If you follow the old rule of rebuilding cross valves upside down,
    your cross-valve stack should be tight as tight can be.  The stack
    I built for my Steinway B thirty years ago still runs evenly, like
    brand new."

What is the "old rule of rebuilding cross valves upside down"?  Thank
you for an explanation.

Barry Dennis