662. Untying

Shabbos 10:7

Any kind of knot that one would be liable for tying would also make one liable for untying; if one is not liable for tying a knot, he is not liable for untying it. If a knot is permitted to be tied on Shabbos, it is also permitted to be untied.

Shabbos 10:8

If someone winds a rope out of palm branches, grass, wool, flax, goat's hair, etc. he is liable for performing a subordinate labor of tying. The minimum amount for which one would be liable is enough rope that would stay wound together without being tied because this is considered permanent. Similarly, unwinding cords is a subordinate labor of untying for which one would be liable – so long as one’s intention is not purely destructive (because the Shabbos labors are all constructive in nature). The minimum for which would be liable is the same as for winding a cord.