I have ties prepared for Shabbat with tie knots ready for shabbat. is it allowed to make the loop smalleer and larger? I have had the same knot for more than a month. it was made on friday and all i do is tighten it and loosen it. A friend told me it might be similar to a knot on the end of an individual Tzitzit thread. thanks Yossi

It's permissible. (Shmirat Shabbat Kehilchata 15, 58)