On Thursday we celebrated Rosh Chodesh Iyar with a special visit and shiur from noted sofer Rabbi Yisroel Kohn. The Shulchan Aruch mentions how often one should check mezuzot, but the lack of instructions for tefillin leads to a lot of discussion on how often they need to be checked. Rabbi Kohn delved right into that discussion and stayed throughout the day to check everyone’s tefillin.