guide pin. See that it sets properly and is not bound by the mortise.

Sometimes a splinter will be found on one side of a key where the lead
has been put in. A piece of any foreign material between two keys
generally causes both to stick.

Where the action is too deep, that is, the keys go down farther than
they ought, place cardboard washers under the felt ones around the
guide pin, or raise the felt strip under back end of keys.

Where the action is too shallow, place thin washers under those around
the balance pin. When this is done, the whole action must be regulated
accordingly, as this alteration will make a change in the working of
the upper part of the action.

2. _The Bottom or Capstan_.--This should be so adjusted that when the
key falls back to its rest position, the point of the jack will just
spring into its place in the nose of the hammer butt. If held too
high, the jack fails to catch in the nose, and the key may be struck
without producing any effect on the hammer. When the bottom or capstan
is too low, the point of the jack will be some distance below the
notch, which will cause what is known as lost motion, it being
necessary to depress the key a portion of its depth before the jack
can act upon the hammer. Depress the key slowly, watching the hammer,
and the fault will be discovered.

After a piano has been used for some time, the keys that are struck
most frequently (those in the middle of the instrument) will be found
to have this fault. The felts under the keys and those which are
between the working parts of the action become compressed or worn so