A lock cylinder is the heart of the Shlage F-Series lock, as the cylinder houses the actual locking mechanism. The key fits into the lock cylinder's keyway, aligning its internal pins to unlock the lock.
Shlage recommends that you use a key gauge to disassemble the doorknob and access the lock cylinder. The gauge is formed from a thin piece of metal with specialized cutouts, tabs and measurements that are used for key maintenance.
Rotate the key 90 degrees in the Shlage lock, then use the tab on the key gauge to press the catch on the doorknob. Pull the knob off the spindle. Remove the key and position the doorknob so the keyway is upright. Drop the rear of the cylinder slightly, then push the cylinder out of the doorknob from the front.