The sandwich man is one of the oldest techniques in modern advertising. Through a century of its history in France (1840–1940), we would like to show how this technique allows us to question the change that takes place between two specific periods of advertising sciences and techniques. The first is typical of the nineteenth century. During this period, advertisements “covered” the modern world; the sandwich man, most often someone “in need,” was then employed to walk the city sidewalks. During the second period, at the beginning of the twentieth century, the first advertisers began to think tentatively about a “blind” consumer psychology. The sandwich man was seen as an ineffective technique that no longer corresponded to the principles of professional advertising.