Rambam IVRIT ve ANGLIT Shofar, Sukkah, vLulav

https://www.chabad.org/library/article_cdo/aid/946093/jewish/Shofar-Sukkah-vLulav.htm¹

One may bind them together with a string, a cord, or with any substance one desires, since binding it together is not a required element of the mitzvah…….THIS SEEMS OFTEN TO BE UNKNOWN