A device for guiding a flap of a closure and, more particularly, a flap of a closure of an article of footwear. More particularly, the invention is directed to an article of footwear in the form of a sports boot equipped with at least two semi-rigid upper elements, i.e., flaps, which overlap during the closing or adjustment of the footwear, thus defining an upper flap and a lower flap, the footwear also being equipped with a tightening mechanism. The tightening mechanism, according to the invention, includes a structural arrangement for ensuring the guiding of the lower flap beneath the upper flap, the guiding arrangement prohibiting the engagement of the lower flap over the upper flap.