Ky, is the Key in its resting position.
c, wherever found, represents a cushion of felt or soft leather upon which the different parts of the action rest or come in contact with each other. Their purpose, as is readily seen, is that of rendering the action noiseless and easy of operation.
Bnc R, shows the end of the balance rail, extending the entire length of the keyboard.
B P, is the balance pin. This is a perfectly round pin driven firmly in the balance rail. The bottom of the hole in the key fits closely around the balance pin; at the top, it is the shape of a mortise, parallel with the key, which allows the key to move only in the direction intended. The mortise in the wooden cap on top of the key at this point is lined with bushing cloth which holds the key in position laterally, and prevents looseness and rattling, yet allows the key to move easily.