Comstock & Cheney supplied makers with this design for leveling the keys without the hassle of removing keys and placing the paper punchings underneath the felt. It is tedious operation made easy by this device. Ahead of the balance rail pin is a small recess in which the other end of a rounded head machine screw is accessible for turning. Because of the threaded screw the key will rise or descend simply by rotating the screw. The screw also serves as the balance point which makes for a smoother arc as the key goes down. Similar in intent to the Steinway accelerated action.