Q. (See question above). If there is a torn page in a sidur and I can’t read the page, can I just join the two parts together during Shabbat davening without attaching them in any way?
What happens if one places the two pieces inside a plastic envelope and that holds them a bit together, and they are used for reading the Shema during the Shabbat Seuda at Friday night?

A. Poskim are lenient when one has not another proper sefer available (Teshuvos Rema 119, Mishne Halochos 6: 89, Shmiras Shabbos K’ 28: 3).

Regarding if the two pieces are placed inside a plastic envelope that helps to hold them together, Horav Shlomo Miller’s Shlit’a opinion is that it should not be used during Shabbos even when needed for reading the Shema.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller, Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a