In an introductory note to this chapter, the Kitzur Shulchan Aruch writes that most Jews are already familiar with the prohibited labors of Shabbos and that he is only addressing common situations with which people may not be familiar. Clearly, the laws of Shabbos constitute an area requiring much greater study than this email alone will allow.
80:47 Before tailors finish off a garment, they join the pieces together with long stitches; when the garment is complete, they remove these stitches. Such stitches may not be removed on Shabbos.
80:48 Some clothes are designed so that a cord or strap must be passed through them, such as a drawstring through pants or laces through boots. When the garment is new, one may not insert the cord for the first time on Shabbos because that constitutes completing the object. (Passing a belt through belt loops is not problematic because it is not considered a part of the same garment - Mishnah Brurah 317:16.) One may insert the cord (though not a new cord – MB 317:18) in a used garment so long as the hole through which he must draw the cord isn't so narrow as to make it difficult. (If one would typically tie a forbidden type knot in order to feed it through the hole, one may not do so even if the holes are wide - MB 317:20).