On a lace closure, the hair is attached directly to the lace base. On a silk closure, there is a small piece of neutral-colored silk on top of the lace that is meant to mimic a natural scalp. People that prefer lace closures like that the closure lays flatter and that the lace and amount of bleaching for the knots can be customized based on the client's skin tone. On the other hand, the knots on silk closures aren't visible and do not require any bleaching or customization, but the material is thicker and it's harder to lay flat. Deciding which kind of closure to use depends on personal preference and desired look.