What is the primary function of a barge board?

The primary function of a barge board is to protect roof edges from weather conditions. This component is typically installed at the gable ends of a roof and serves to shield the exposed edges of the roofing materials from wind, rain, and snow, thereby preventing water infiltration and damage to the underlying structure. By adding a protective layer, barge boards help ensure the longevity of the roof and maintain its structural integrity. They also contribute to the overall aesthetic of the building, often framing the roofline in a visually appealing way.

The other options don't accurately describe the primary function. Supporting roof rafters, enhancing ventilation, or holding roofing tiles pertains to different structural elements or components and does not capture the main purpose of barge boards.