I have tried several techniques (grid etc) for finding the nodal point and I find that my old eyes (66 years) have problems using them. I developed a rail sight that seems to work for me. The rail sight is a C-channel with two screws: one short screw and one long screw. The screws are at each end of the 24 inch C-channel rail. I line the rail sight up with my camera and focus on the short screw while aligning the long screw with the short screw. The long screw sticks up above the short screw. If I rotate the camera clockwise and the long screw moves counter clockwise, then I move the camera forward. Actually, if the long screw moves the same direction as the camera body, then move the camera forward. If the long screw moves the opposite direction of the camera body, then move the camera backward. I have attached three pictures. A side view of the setup, a centered sight view and an off center sight view. Is this correct, or am I missing something?