This paper describes how to use signs as a part of the work task scenarios with service robots. The signs are introduced as an alternative or complementary tool for passing information of the task plan of a work task from the human operator to the service robot. The signs can be used for pointing a direction, bounding an area, marking a route, or defining location of a target. There are two kinds of signs, passive and active. The passive signs have all the information in their appearance. In active signs the information content can be modified, for example with radio communication. Moreover, active signs can be equipped with sensors such as GPS-receiver and compass to measure their location on the map. One of the advantages of using signs to control work tasks is usability. The signs are just carried to the working area and no other actions are needed. Tests in real outdoor and non-structured environments with the WorkPartner robot are realized and experimental results are shown.