Final answer:
A Port Hand Day Beacon is a maritime navigational marker kept on the left side of a vessel, identifiable by letters and odd numbers, to ensure safe passage.
Step-by-step explanation:
The term Port Hand Day Beacon refers to a navigational aid encountered in maritime navigation. It is a specific type of mark that helps sailors and boaters determine their position and safe course while at sea. This beacon is designed to be kept on the port (left) side of a vessel as it travels upstream or enters a harbor. The identification types for this navigation aid are signified through letters and odd numbers, which allow boaters to easily recognize this marker during daylight hours, ensuring they can safely navigate waters without veering off course.