Gas mains are underground pipes that carry gas from one point to another for general use. Common materials for gas mains are steel and plastic, with sizes ranging from 1 1/4 to 24 inches depending on intended use and pressure requirements. Installation involves planning the route, breaking pavement, laying the pipe, pressure testing, purging air from the line, backfilling, and restoring pavement. Proper handling, storage, joining, and safety procedures must be followed during the entire installation process.