In the recent discussion of mandolin rails for a piano, there is one
factor that I haven't heard mentioned -- or perhaps I missed it.  I
seem to remember that the mandolin rail should NOT be arranged such
that the metal clips are positioned between the hammers and the
strings.

The reason is just as Eric mentions.  If the hammer traps the clip
against the string, it will eventually wear all three parts.
Descriptions of rail design which I saw years ago have the clips
positioned just below the place where the hammer strikes.  Thus, the
hammer strikes the leather finger just above the clip and flips the
clip lightly against the string.  I've had our mandolin rail this way
for over twenty-five years, and it sounds great and has produced no
wear.

Craig Smith
Upstate New York
(The new organist played "I Will Not Pass This Way Again".  There was
grateful applause from the audience.)