Am I permitted to insert a new shoelace into a shoe on Shabbos?

One could easily think that there is nothing wrong in inserting a shoelace into a shoe, being that it does not involve craftsmanship or cutting or any other melacha. Nevertheless Chazal tell us that it involves ???? ???  – making a k’li.

We find the gemora Shabbos 48a saying that one is permitted to reinsert feathers into a pillow they were previously in but not to introduce them into a pillow for the first time. The reason behind this is because the bond between the feathers and the pillowcase form a k’li. The same applies to the shoe:

The shoelace complements the shoe and makes it functional therefore the threading of the lace into the shoe is ???? ???. [1]

Does this only apply to new shoes and new laces?

This halacha applies equally to old shoes, new ones, old laces and new ones. In other words one may not replace a torn shoelace with a new lace or with an old one, regardless of whether the shoe is a new one or an old one. The logic of ???? ??? equally applies because with all these cases a lace and a shoe form a k’li.

Am I permitted to swap shoelaces, i.e. to transfer shoelace from shoe A and insert it in shoe B?

No, you may not, for the same reason. Even though both shoes are functional, by introducing lace A into shoe B you are again making a k’li. If a shoelace came out you may rethread it into the same shoe because the shoe and the lace have already formed the k’li.

Is this halacha applicable in other areas as well?

Inflating a soccer ball for the first time invokes the same prohibition. This is because a soccer ball is blown up once and introducing air into the ball forms a k’li. This is only true of items that are inflated and are not deflated subsequent to use. A rubber duck, for example, is not subject to this prohibition because it is inflated prior to use and deflated after use. This last halacha is based on the Magen Avraham (317:7) who says that one may thread a belt into trousers on Shabbos because the belt is removed after wearing.

Accordingly it is permitted to thread a ‘wrong’ color shoelace (for lack of a more suitable one) for the first time on Shabbos because it will be removed after wearing. [2]

Likewise if the shoelace would be thread in such a way that one would not leave it as it is, it is permitted.

The idea behind this is that when the two items are permanently united we say that a k’li has been formed but when they are not permanent, we say that one item is merely aiding the other and the two together do not form a k’li. [3]

If the cord in my pajama trousers came out am I permitted to restring it on Shabbos?

According to the Mechaber one may restring a shoelace, a sandal strap and a hood lace provided that he does not tie a knot in the string. [4] He bases his ruling on the Rambam.

The Mishna Berura [5] and many other poskim base themselves on the Tosefos and the Rosh who hold that one may rethread when two conditions are complied with:

1)        The thread is easy to thread.

2) One does not usually tie a knot subsequent to such a threading.

Accordingly each threading or stringing must be judged individually.

Lacing the hood is rather arduous and would therefore be forbidden to lace on Shabbos. The same can be said of the pajama trousers. Accordingly, even though one is merely restringing the item and as such ‘making a k’li’ would not apply, since it is difficult to restring it, it is forbidden to do so. [6]

Likewise if subsequent to stringing one usually ties a knot to prevent it from slipping out, it is forbidden to insert the string or lace.

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[1] M”B simon 317:18.

[2] SS”K 15:60.

[3] See the sefer Binyan Shabbos pages 158-159.

[4] Shulchan Aruch simon 317:2.

[5] M”B 317:20

[6] The Shulchan Aruch HaRav explains that when something is hard to restring it is similar to Makeh B’patish – stringing it for the first time.