701. How Tzitzis Strings Should Hang
Tzitzis strings must be tied so they are notef al hakeren (dangling alongside the corner). They should not hang straight down toward the hem of the begged (garment), nor should they be secured diagonally so that they hit the corner straight on, but should list towards the side of the begged and then stream vertically along the edge to the corner.
The halachic definition of keren (along the corner) includes an area within the edge of the begged, equivalent to melo kesher gudal (from the tip to the first knuckle of the thumb), just under three centimeters. This is a limitation on how far the tzitzis strings may stray upwards from the corner (and according to some opinions sideways too)—and still optimally fulfill the requirement of hanging “al kanfei bigdeihem” (on the corners of their garments).
The position of notef al hakeren (or at least arranging the strings so it is always a possibility) should be maintained throughout tzitzis wear, not just when they are first tied—though if they move outside the vicinity of melo kesher gudal while being worn, they are still considered kosher. Tzitzis wearers who “tuck in” should be careful that the strings remain affixed in the correct way while undercover, and extra special care is required for those who hide the tallis katan (lit. small tallis—i.e., the tzitzis garment), but leave the tzitzis dangling out.
Many have the minhag (custom) of placing two holes angled towards the corner of the tallis katan through which the strings are tied. This design helps the tzitzis strings hang appropriately, notef al hakeren, and prevents them from creeping too high or inward. The Siddur Harav recommends placing a second small hole right on the side edge of the tallis gadol (large prayer tallis) also for this purpose.
When wearing the tallis gadol for davening (and perhaps swaying in such a way that the tzitzis swing), best effort should be made so the tzitzis strings retain the position of notef al hakeren.