A 5×5 lace closure is a type of closure used in hair extensions that consists of a five-inch by five-inch piece of lace with hair attached. The lace is then placed over the scalp and secured with tape or glue. Closures are often used to give the illusion of a natural hairline and can be styled in various ways. 5×5 lace closures are one of the most popular types of closures on the market due to their versatility and natural appearance.