Store and forward networks predate the use of computers. Point-to-point teletype equipment was used to send messages which were stored at the receiving end on punched paper tape at a relay center. A human operator at the center removed the message tape from the receiving machine, read the addressing information, and then sent it toward its destination on appropriate outbound point-to-point teletype link. If the outbound link was in use, the operator placed the message in tape in a physical queue, usually consisting of a set of clips or hooks.