Shoelaces (also shoestrings, shoe laces or boot laces) are a system commonly use to secure shoes. The shoelace can be untied and loosened, permitting the shoe to open wide to admit the wearer's foot; it can then be tightened and knotted into a bow shaped knot. Shoelaces did not become widely popular until the 20th century. Previously shoes were slip-on, buckled, or buttoned. Buttoned shoes used a special tool, a button hook, to close the buttons, but this was slow and difficult.