A mobile billboard is a device within the marketing practice of advertising on the side of a truck or trailer that is typically mobile. Mobile billboards are a form of Out-Of-Home (OOH) Advertising. Radio, static billboards, and mall/airport advertising fall into the same category. Using a mobile billboard for advertising is an advertising niche called mobile outdoor advertising.Most mobile billboards are dedicated, customized trucks with large, but narrow, bodies for posting the advertisements. Some of these dedicated units offer features such as external sound systems, illumination, and hot/cold boxes for product sampling.