This might be waaay old news for the avid crafters out there, but for all of you that are just getting in to jewelry making ill start doing posts about easy techniques to get you started (Crafting 101).
To make this lock all you need is some scraps of cotton thread (not waxed) and some clear nail polish to seal it. I mostly use it for bracelets, its super easy to do and easy adjustable so you dont need anyones help to put on your bracelets (am I the only one that struggles with everything except bangles??).
Tip: you need to have a knot or bead at the end of each of the sides of the bracelet, otherwise they will slipp through the lock.