[ Randolph Herr described a regulating method in 021231 MMDigest. ]

Renner makes an offset screwdriver for turning these rocker arm screws.
It is called a Bechstein Offset Screw Driver.  It makes it relatively
easy to adjust the screws with the keys in place.  The blades on the
opposing surfaces are reversed for quickly addressing the direction of
the slot in the screw head.

Regards,

Jon Page,  piano technician
Harwich Port, Cape Cod, Mass.