If you find that the glass ‘clicks’ at “A” it should do the same at “D” when you reverse hands. Conversely, if it clicks at “B” it should also click at “C.” If that’s the case you have learned two things: you are holding the glass properly and the fork needs to be adjusted in the Y-plane. If you don’t get any “clicking” try putting your thumbs at “A” and “D” and pushing them alternately, then repeat the procedure with your thumbs at “B” and “C,” in each case without holding the glass against the fork tubes other then where you are pushing with your thumbs. It may be that the tubes are so far out of alignment that the slight flexing of the glass by holding one side and pushing at opposite corners will not cause the “clicking.” If there are no clicking sounds at all and the glass is visually against the fork tubes along its entire length on both tubes, then the tubes are aligned in the Y-plane. Lucky You!