A rain gutter is a narrow channel, or trough, forming the component of a roof system which collects and diverts rain gutter installations. by the roof. The main purpose of a rain gutter is to protect a building’s foundation by channeling water away from its base. They also help to have erosion control, to prevent leaks in basements and crawl spaces protect painted surfaces by reducing exposure to water, and provide a means to collect rainwater for later use in years past.