First you will need to understand a closure. A closure is a small piece of lace. Like a real piece of lace, like clothing. On the lace there are naturally tiny holes from making the lace. In between those holes we take 1-3 strands of hair and make a knot around the hole. That knot you can see if you look really hard. A stylist can bleach the knot, making the knot and the lace change color to a blonde shade resembling a scalp color, and no longer seeing the knot like an unbleached knot.