ame time, work the jack back and forth.
This will generally free it if the jack-spring is all right.

3. _Jack_.--As in the upright, the behavior of the jack depends
entirely upon the surrounding members. A very common occurrence in the
square piano is a broken jack-spring. This spring is concealed in a
groove on the under side of the bottom, with a linen thread leading
around the end of the jack and held fast by a wooden plug. If the
spring is found to be long enough, drive out the plug, attach a new
thread to the spring, and fasten as before. If a new spring is needed,
one may be made by wrapping some small wire round a piece of music
wire of the right size.

4. _The back check, hammer stem and regulating button_ are subject to
the same faults as their counterparts in the upright, which may be
remedied in the same way. Bridles and hammer springs are not needed in
the square, as the weight of the hammer, moving in a vertical
direction, is sufficient to bring it to its rest position.

5. _Hammers_, when made of felt, will of course require the same
treatment as those in the upright. In many old squares the hammers are
built up of buckskin. If this becomes beaten down hard, it is well to
cap the hammer with a new soft piece of buckskin, gluing only at the
back ends.

6. _Butts and Flanges_.--A click just as the key comes up, indicates
that the felt cushion, against which the jack rests, is worn out and
must be replaced.

In all square actions the center pin, in the butt, is held by friction
alone, but rarely gets loose; if it should be found loose, put in a
larger pin.

The flange, shown in the cut, is what is called a split flange. By the
set screw T, the jaws can be regulated so that they neither clamp
the center pin so tightly as to make the action sluggish nor so
loosely as to let the hammer wabble.

If the bushing cloth is found to be badly worn, it is better to put in
new, which must be done neatly, or the result will not be
satisfactory.

Hammer flanges, like all other wooden parts, shrink away from the
screw heads and allow the hammer to drift to one side or rattle. While
the action is in the piano, strike the keys to see if there are any
that strike improperly. Mark the keys so as to indicate just what the
trouble is, so that you will know how to remedy it when the action is
out. If the hammers are set so close that they rub against each other,
you may have to cut off a slight shaving of felt, but thi