Q. If someone has a tzitzis garment that has buttons on the side (looks like a vest but the buttons are on both sides for closing it when it is cold) does the garment become disqualified when buttoned, and it will not revert to kosher when later unbuttoned?

A. Horav Shlomo Miller’s Shlit”a opinion is that since buttons or for that matter a zippers, do not constitute “tefira” or sewing for Shabbos purposes, they also don’t annul or invalidate the qualification of a garment to be fit for tzitzis. Although it may be better not to use it buttoned, you do comply with the mitzvah at that time.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a