A distribution network operator, also called a DNO, is a distribution gas or electric utility that focuses solely on construction, operation, and maintenance of a distribution system. A DNO provides transport services for gas or electricity but does not sell supply to customers. Supply is provided by retail marketers and/or community aggregation. Utilities that follow the DNO model must create all their profits through return on distribution assets. To attain growth, utilities often pursue growth by becoming larger through horizontal mergers with other distribution utility systems.