The pilot director light (often referred to as PDLs or PDIs [Pilot Director Indicators]) are seen here swung out from the belly of a KB-29.
Here is an interesting image showing the pilot director lights of the Boeing KB-29. In this image, the director light panel has been swung out from under the belly of the aircraft, presumably for maintenance. The director lights illuminate to give the receiver aircraft’s pilot information on his position in the air refueling envelope. One set of lights indicates his forward-aft position and the other set indicates the up-down position. All subsequent tanker aircraft including the KB-97, KC-135, KC-10, and now KC-30 and KC-46A include a similar arrangement of pilot director lights.