I have a tear in one of my pants and a button fell off of one of my kids blouses. May I sew it during the nine days?
Explanation: The Rishonim and Poskim rule that it is forbidden to fix [i.e. make] new clothing during the nine days. Likewise, the Talmud and Poskim bring that the women are accustomed not to weave the warp during the nine days as the warp is called the Sheti, and on Tisha B’av we lost the Even Hashetiya. Based on this the Achronim rule that it is forbidden to remodel old clothing beginning from Rosh Chodesh Av, throughout the nine days. Nonetheless, it remains permitted to sew a loose stitch, or sew a tear of an already worn pair of clothing, or resew a button throughout the nine days, even in the week of Tisha B’av. The reason for this is because the main restriction is specifically regarding making fixing new clothing and not regarding repairing old clothing.
Sources: See Michaber 551:7-8; Bach 551; Kneses Hagedola 551:10; Elya Raba 551:16; Bigdei Yesha 551:8; Moed Lekol Chaiy 10:18; M”B 551:46; Kaf Hachaim 551:99; 551:107; Orchos Rabbeinu 2:129; Ben Ish Chaiy Devarim 10; Piskeiy Teshuvos 551:29 footnote 156; Nitei Gavriel 37:2