About the middle of the 15th century, the breastplate of the cuirass was made in two parts; the lower adjusted to overlap the upper, held together with a strap or sliding rivet in order to add flexibility to the advantages plate armor had over mail. In the second half of the 15th century, the cuirass was occasionally superseded by the brigandine jacket, the medieval forerunner of the flak jacket. In essence, the brigandine jacket was constructed of metal plates sewn into a fabric jacket. The fabric was generally a rich material, and was lined throughout with overlapping scales of metal which were attached to the jacket by rivets, having their heads, like studs, visible on the outside.