1) ''Tikkun Maneh'' - ''completing the object'' is an activity which involves putting the finishing touches on an object and is prohibited as a derivative (Toldah) of the Melacha of ''Makkeh Be'Patish'' - ''pounding with a Hammer''. 2) This applies to reinserting the regular cord or string, however, to insert a new one would be forbidden. (See Mishna Berurah 317:18). Passing a belt through new trousers isn't prohibited, because a belt is not generally permanently connected to them, but rather is made to be removed and reinserted. (See Mishna Berurah 317:16). 3) Where it's customary to tie a Shabbat forbidden knot on the end of the cord, to help feed it through, even if the holes are wide so that it goes through without difficulty, it's still forbidden because the sages were concerned that one might come to tie the knot inadvertently on Shabbat. (Mishna Berurah 317:20).

1) One of the 39 Avot Melachot ((prototype prohibited activity) is ''Sewing'' - ''Topher''. Any act which involves joining of two items by means of a binding agent (like thread, glue, tape, etc.) might be prohibited as a derivative (''Toldah'') of ''Sewing''. It would also be forbidden to secure a loose button by tightening the thread. Regarding the use of a safety pin, there is a dispute among the authorities as to whether it's considered an act of sewing. Since we are dealing with a Biblical prohibition, we follow the stringent view; however, the use of safety pins is permitted in the following circumstances: a) It's permitted to pass a safety pin through two pieces of fabric once (that is, the pin pierces each piece of fabric only once, and then emerges on the other side); b) If one inserts the safety pin in a way that one will be assured to remember to remove it within 24 hours, then one may even pass the pin through the items twice; c) In cases of necessity, where none of the aforementioned methods are feasible, one may rely on the authorities who rule that safety pins are permissible no matter how one uses them.

לפעמים איזה תפירה מתקלקלה ומתפרדים החתיכות קצת זה מזה ומושכין בחוט בתפירה והן מתהדקות ומתחברות אסור לעשות כן בשבת משום דהוי תופר

1) One of the 39 Avot Melachot (prototype prohibited activity) is ''Tearing'' - ''Koreah''. Tearing or cutting any soft material, or separating two items that were sewed or glued together, is prohibited under the category of ''Tearing''. If the act of tearing serves a constructive purpose, it's prohibited Biblically, if not, it's a Rabbinical prohibition. Tearing destructively is, however, permitted in order to obtain something necessary for the honor or enjoyment of Shabbat. For example, it's forbidden to open a cereal box at the top in the usual manner, because that would be a constructive act which enables the box to be closed and reopened easily. However, one may cut open the box in a way that makes it unfit for storage (one must be careful not to cut through any letters, words or pictures). Things which became attached inadvertently are not subject to the prohibition against ''Tearing''. 2) If, however, the pages of a book are joined on the top because they were never completely separated from each other during the binding process, it's forbidden to separate them on Shabbat (Mishnah Berurah 340:45). In cases where it's allowed to separate the pages, one should be careful not to tear through, erase or even uncover any letters or words.