Horseshoes appeared around 900 A.D., which may have been a Roman innovation, and are common at sites from the 1st century B.C.. However, it is often thought to be the iron heel of a leather shoe. From about 85 to 54 BC, common horseshoes were made of iron, very light, and stamped with a pierced nail hole from one side. The edges of the horseshoe often had a corrugated profile, and the unfastened ends were bent into a non-slip spur, which, along with the nail head, kept the horse's hooves solidly on the ground, useful for both field cultivation and pulling for transportation. This horseshoe was used until the Middle Ages. The invention of horseshoes for the agricultural revolution made a great contribution.