Sometimes you will find one key warped so that it rubs on the next, in which case, plane off a slight shaving to free it.  Sometimes changing the position of the guide pin will straighten or level the key and make it work all right.

The balance pin is subject to some of the same difficulties as the 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 that the jack will be found to set so low that there will be lost motion in the key.  In this case, loosen one of the screws in the bottom and turn the other down so as to move the jack upward until nearly all lost motion is taken up.  A little play is generally necessary, but very little.  In case the action has a capstan, simply turn it upward.

3. Back Check.—­Blocking is most usually caused by the back check being too near the back catch, so that when the key is struck, the back check holds the hammer against the string.  This should be seen after raising the bottom or capstan as above referred to.  It will be observed that when this is done on account of the wear of the felts, the back check will stand much nearer the back catch than it did before, and will need bending back so as to give the hammer plenty of “rebound.”  A steel instrument with properly shaped notches at the point, called a regulator, is used for bending wires in regulating the action.  See that the wires stand as nearly in line as is possible.  In old actions that are considerably worn, however, you will be obliged to alter some more than others.