The hole for inserting the tzitzis must be in the area called 'kanaf' near the edge of the garment. This area extends three 'finger-width' from the edge. There are several opinions about to how measure this space. It may be three times the width of the average thumb, three times the width of the thumb at its narrowest point, or the combined width of the pinky, ring and middle fingers. The poskim discuss whether the hole should be within the area of three finger-width from the edge or exactly three fingers from the edge. The proper way to fulfil all of the opinions above is to place the hole within three fingers of the smallest of the above opinions.
In order to keep the hole in the area of kanaf and not on the actual edge, the hole should be removed from the edge at least one kesher godol - i.e. the space between the thumbnail and the first joint. This is approximately 4-5 centimeters. The practice of the Chazon Ish was to make the hole 4.5 centimeters from the edge.
The popular custom is to make only one hole for inserting the tzitzis onto both the talis gadol and talis koton. There is a custom to make two holes based on an opinion of a Rishon cited by the Beis Yosef and based on the practice of the Arizal. Both holes should be within the three finger range, close to one another, and positioned side by side. According to some poskim, the outer hole may be within the kesher gadol mentioned above. The tzitzis should be positioned nearer to the outer hole so as to dangle on the corner.
The pasuk says "they shall make for themselves tzitzis," from which Chazal understood that the wearer must own both the cloth and the tzitzis in order to fulfill the mitzva.
If someone stole tzitzis and attached them to a garment, and afterwards paid for them or received them as a gift, it is questionable if they are pasul. This is because of the rule of ta'aseh v'lo min ha'asuy, which requires that the tzitzis strings be placed on the garment in a kosher manner. The strings in such a case should be removed and re-knotted.
Generally, a thief is required to return whatever item he stole. If, however, the item was significantly altered, the thief is considered to have 'acquired' the item; he does not need to return the original item but can pay for it instead. This is known as shenui ma'aseh.
If the tzitzis hole tore
Reinforcing the hole and hem
The position of the hole on a garment with tassels or fringes