Ah, that collapsed nail joint. If we overcorrect, we have very tense students whose overcurved , tight fingers produce uneven passagework. If we wait a bit and the technique is developing nicely otherwise, the problem can resolve itself. In the case of very collapsed nail joints, it is often the case that the student is not completely clear where the joint is. For this reason, I recently asked a student to put a sticker directly on the nail joint. This activity clarified her thinking and she made some good improvements. She enjoyed this activity so much that she provided her own stickers the following week. Best of all, no nagging required!