In hilchos tzizit siman 11, se’if 15, it states that the tzitit should fall on the edge (not hang down). Also, many are concerned that the tzitis should not hang on the point of the edge. Can someone use tape to make sure the tzizit are properly positioned? Is there any concerns about using tape in this manner?
The usual method for ensuring that the tzitzis hang correctly is to make the first knot a little tight, thereby ensuring the strings don’t fall from their correct position on the edge (see Biur Halacha, 11, s.v. le’orech, concerning the correct location for strings). Tape can also be used, and this would not invalidate the tzitzis.
See Mishnah Berurah, end of 11, who rules that poskim agree that adding something extra is acceptable.