I heard that one is forbidden to tie a sailor’s knot on Shabbos, but are not all knots forbidden?

In order to answer your question we need to lay down the foundation of this sugya. The pertaining Mishna and gemora can be found in Shabbos 111b-112a. We find that the major Rishonim differ over the understanding of the sugya and hence the ramifications greatly vary.

The Halacha subdivides the tying of knots on Shabbos into three categories: 1) Knots that are Biblically prohibited to tie, 2) Knots that are Rabbinically prohibited to tie and 3) Knots that are permitted to tie.

Ossur mid’oraisso: the gemora says – ???????? (bid’ushkepi). Rashi explains that the leather worker would insert a strap into the shoe and tie it permanently into place. Since this knot is a permanent one, it is ossur mid’oraisso.

Ossur mid’rabanan: the gemora says bid’rabanan (the student’s shoes). Rashi explains that the students would tie their shoe straps loosely to their legs enabling the shoes’ removal without having to untie the knots. Nevertheless they were not permanent knots, because when walking in mud they would untie the knots and fasten the straps tightly to their legs so that the shoe would not stick to the mud and come off.

Permitted: ??? ????? (B’nei Mechoza). Rashi explains that the people of Mechoza were meticulous with their clothing and would tie the straps tight to the point that they could not be slipped off the leg. Therefore it was not a permanent knot since they would have to fasten and unfasten the shoe straps to their legs on a daily basis.

The Rif and the Rambam add another factor – craftsmanship. They see in the sugya that for a knot to be Biblically prohibited it must be the type tied by craftsmen. The underlying feature of such a knot is its strength. [1]

So where does the sailor knot come in?

The sailor knot is a craftsman’s knot par excellence and would definitely contribute towards a perpetrator being guilty of a Biblical transgression. However time is a factor as well, as we will see.

The other factor is time and according to Rashi and the Rosh it is the only factor.

A knot tied forever – kayama – is ossur mid’oraisso.

Longer than a week or 24 hours (two opinions) is ossur mid’rabanan.

Less than a week or 24 hours (the respective opinions) is permitted.

The synopsis is as follows:

	Permanent	Semi permanent	< 24 hours < a week
Craftsman’s knot	Biblical according to all	Rif  and Rambam  – Rabbinical	Rif  and Rambam  – Rabbinical Rashi Rosh – permitted
Layman’s knot	Rif  and Rambam  – rabbinical Rashi Rosh – Biblical	Rif  and Rambam  – machlokes [2] Rashi Rosh – Rabbinical	Permitted

 

There are two opinions as to the permitted time factor and L’chatchila one should not tie even a simple knot on Shabbos if he intends untying it after 24 hours.

Which of the above opinions is the halacha?

The Shulchan Aruch (Mechaber) rules according to the Rif and the Rambam and The Rama rules according to Rashi and The Rosh, at least l’chumra. Accordingly one may only tie a simple knot within the permitted time bracket.

Are most knots permitted because after all most knots are not craftsmen’s knots?

Things are not so simple. The poskim hold that a strong double knot is classed as a craftsman’s knot due its sturdiness and strength; hence one may not tie a double knot even for less than 24 hours.

What about a double knot tied in a woman’s kerchief or the knot in the handkerchief tied around one’s neck, are they also forbidden?

Since the main feature of a craftsman’s knot is its strength and these particular knots are not tied sturdily, one is permitted to loosely tie them. [3] This would seemingly not apply to tying shoelaces in a double knot owing to the fact that they are fastened tightly.