Superior performance screws for countersunk head caps Zinc, which has a zinc-plated finish for superior corrosion protection, is also known as \”Countersunk bolts,\” \”Allen bolts,\” or \”Socket head cap screws.\”It can be used to fix steel to steel or timber to steel in construction with a matching hex nut, or it can be used for high strength bolting into threaded components and assemblies in manufacturing and engineering.