How to wear a Tallis Katan on Tishe Beav:

Tallis Katan-Blessing and how to wear:[1] On Tishe Beav, the Tallis Katan is worn under one’s clothing without a blessing.[2] [Other Poskim[3] however rule a blessing is to be recited if one did not wear the Tallis Katan at night and is now putting it on in the morning. Practically, one is to sleep with a Tallis Katan and continue wearing the pair the next day in order to avoid this issue.[4] Some tuck in their Tzitzis and do not allow the fringes to show until midday.[5] However, many wear the Tzitzis out as usual.[6]]

Kissing the Tzitzis:[7] The widespread custom is not to hold or kiss the Tzitzis by Baruch Sheamar and Shema.

Tallis Gadol:[8] The custom is not to wear a Tallis Gadol by Shacharis.[9] By Mincha, one wears the Tallis with a blessing. ^[10]

[1] Michaber 555:1; Tur 555; Maharam Merothenberg Semachos 60; Iggur 846; Levush 555:2; Chayeh Adam 135:18; Luach Eretz Yisrael

Other customs: The old custom of all Ashkenaz was not to wear a Tallis Katan at all on Tishe Beav. [Tur ibid in name of Maharam MeRothenberg]

[2] The reason: As the verse in Eicha 2:17 states “Betza Imraso” which means that the fringes of G-d were belittled. [Tur ibid in name of Maharam ibid; Levush ibid]

[3] M”B 555:2 in name of Pischeiy Olam; Siddur Yaavetz

[4] Halichos Shlomo 1:3 footnote 34

[5] As writes Michaber ibid “under the clothes” and so is the custom in Brinue; Leket Yosher p. 110

[6] Nitei Gavriel 58:7; Rav Ashel Lemel Hakohen

[7] Nitei Gavriel 58:22; Piskeiy Teshuvos 555:2

[8] Michaber 555:1; Ramaz 107; Shaareiy Teshuvah 18:4

Other opinions: Some Poskim rule one is to wear Tallis and Tefillin by Shacharis as usual. [Birkeiy Yosef 555:1; Shaareiy Teshuvah 555:2; Minhag of Rashash and Beis Keil; Kaf Hachaim 18:16 that so is custom in almost all Shul’s in Jerusalem; Rav Yaakov Yosef that so should be followed in Sefaradi Minyanim of Bnei Torah] The Rebbe Rashab wore Tallis Gadol before Shacharis and wore Tefillin during Shacharis, although he Davened in private in order not to be noticed by the public. [Sefer Haminhagim p. 97]

[9] The reason: This is based on the Midrash which states Hashem removed His Tallis and Tefillin by the destruction. [See M”B 555:1]

[10] Michaber 555:1