Thanks for the replies. I see the logic of using w/d sandpaper on glass instead of the 120 stone, if one is going to be lapping the 120 stone on glass anyway. And I do have access to diamond plates and SiC powders. I was just wondering about using the 120 as an in-house lapping stone. Maybe 1000 and 4000 would stick together, while the 120 would have enough texture to prevent this from happening if used to lap the 1000 and the 4000?