MB3 131b: Halachic Differences in Knots on Shabbos (317:1 Part 2)

Tying a knot on Shabbos if it isn't permanent and is not professional. A knot which can be tied can be untied. If a knot may be untied on Shabbos but you are unable to untie it, you can cut it. Tying a non-permanent professional knot for a mitzvah purpose. Double knots and tight knots.