Tying a knot to make or repair a necklace is not as easy as it may sound. The person doing all the tying must be able to use both hands with almost equal flexibility and patience.
You must understand what kind of material the necklace is made. If it is made of cord, string, yarn or any such material, there should be no problems. If the necklace is made out of metal or plastic, knotting it may not be so easy.
Once you have identified the material, you can begin. Place a charm, pendant or other decoration onto the necklace. Make sure it is in the centre of the necklace with the ends of the necklace free.
Take both ends of the necklace and place together. Tie it together using the same technique used to tie shoelaces. This may not work with metal or tough, slick plastics because the tie easily slips through itself. For particularly sturdy plastics and metals, you may need to used a double knot. Aesthetics may be an important factor for some in which case the shoe-tie knot won't be suitable.
A double knot is very strong and hard to undo. It's preferable for the necklace to slip over your head. To remove the knot, however, turn the necklace around so that the knot is in front of you. This will make it much easier to untie.
If you can't tie a knot yourself, have a friend do it.
Never tie a necklace too tight around your neck in a double knot. Always ensure the knot is tight enough before you carry on with your day.