<HTML>Hello Roy,    This is standard on most  K&B  grands.  This bolt/screw is made to fit a tuning hammer. The action  does not shift, instead the hammer line raises when the soft pedal is engaged. You will find also that these actions looks different from most. Don't let this scare you.       It is my guess that this bolt/screw was an attempt to discourage people from  repairing their own pianos. Old piano guy! Jack</HTML>