International companies in Colombia and El Salvador are learning what it takes to do business with the low-income communities in their own backyards...ColCerámica...which makes sanitary devices like toilets and sinks...has now come out with a line of new products to serve [low-income customers]...who typically have modest houses in need of renovation...Salvadorian cement company Cessa, a Holcim subsidiary, is making its technology available to small-scale brick producers to help improve their productivity.