You should not tie objects that normally have a real knot even with a simple knot as you might forget .

Chapter 317 Section 5

A knot and a bow on top of it is permitted if you plan to open it in 24 hours.

Chapter 317 Section 6

If you tie with a permissible knot a string on 2 sides of a doorway, we do not suspect that one knot you will leave for a long time and making it a prohibition.