One may not tie a double knot even if he plans to untie the knot on the same day. Since this is a strong knot that can remain intact for an extended period, it may be that it is comparable to the knot of a craftsman (Shiltei Giborim). According to some Rishonim (Rif and Rambam), tying such a knot for the short term is rabbinically forbidden. All this refers to a tight double knot, which one might use to tie his shoes or to close a garbage bag. But a woman may tie a head scarf this way, since the scarf is not pulled tight. Those who are especially meticulous are stringent and do not use a double knot to tie their head scarves.
If it happens that one’s shoes were tied with a double knot and this causes him anguish, he may undo the knot.[11]
One may not tie off the end of a thread even with a single knot, the way one does when sewing or when tying the end of a tzitzit string. Since this knot is strong, it might be considered a craftsman’s knot. According to some poskim, if it is meant to be temporary it is rabbinically prohibited, while if it is meant to be permanent it is prohibited by Torah law (Smag; Rema 317:1). Similarly, one may not use a tight knot to tie a plastic bag with food in it, but one may use a bow knot or tie the bag handles together with one tie.
