Final answer:
Gold hash marks on the left sleeve of a military dress uniform indicate years of service, with each stripe representing a set period depending on the military branch.
Step-by-step explanation:
Gold hash marks on the left sleeve of the dress uniform represent years of service in the military. Specifically, these hash marks, also known as service stripes, are worn by members of the United States military to signify the length of service they have completed. Each stripe traditionally indicates a standard period of service, which can vary depending on the branch of the military. For example, in the U.S. Navy and Coast Guard, each gold service stripe represents four years of service, while in the Army and Marine Corps, each stripe often represents three years of service.