Safety locks

You can also make different colour combinations of the safety clasps by putting in a counterpart of another colour! BPA-free locks have a 2mm hole.

You can use them on cotton twine, polyester twine and even metal wire by putting a 4mm bead on the end of the wire to prevent the wire from coming out of the hole. The safety lock opens when the rope is pulled out. The safety lock opens when it is folded down from the ends. It's like folding a crispbread...it also works the same way, if you pull down on the jewellery, the safety lock opens.
For cotton and polyester twine, a knot that stays inside the safety catch is enough.