The keyframe is the bottom part of the keyboard assembly. You can see the two rows of pins that are installed into it. The keyboard's keys have holes drilled into them that line up with these pins. The keyboard is placed onto the keyframe and the pins keep the keyboard's keys in their proper position. Small felt and paper punchings are placed onto the front row of pins to control the height of the keys. The more punchings, the higher the keys will be at their front ends.A strip of felt will be placed behind the rear row of pins. This felt will silence the keys as fall back to their rest position. Small slits are cut into the rear of each key that are just wide enough to let the rear pins slip through them. This keeps the keys straight and doesn't allow them to drift left to right.