When horse owners call up Sam Gubera, they expect to hear a man on the other end of the phone. In this case, Sam is a woman and a farrier. At 27, she’s one of the few women in the job field in the San Francisco Bay area. Having taken horseback riding lessons since she was a kid, Gubera’s break from horses in college made her miss being around them. After a quick call to the farrier who serviced her childhood horse — also a woman — Gubera enrolled in the Pacific Coast Horseshoeing School in Plymouth, Calif.