One good way to checkmate is to use two rooks, or a rook and a queen to force a lone opposing king to the edge or the board. If one rook defends an entire file then the opposing king can't cross it. If you use the other rook to control the next file, you can force the king to the edge one step at a time until you checkmate it. Picture a position with White rooks on g1 and h2 and a Black king on h5 in checkmate. This mate also works by forcing the king to the first or last rank.
