The private security is a growing sector in Brazil, as can be observed in the last years, with the companies and workers' development in this department. Although its growth, few are the studies that approach the work conditions which these workers are submitted. Following this bias, it was done a research centered in the study of security guard's work in a Federal University, in the interior of Minas Gerais state. It was used and applied the presumed ideas of ergonomics analyses and the concept of intermediary objects, that offers the possibility to workers contrast the represented situations lived by themselves. These way, they could participate. As result, it was possible to verify that the intermediary objects could bring up to surface as much the identify of real works' contradictions - Like the number of electronic points that exists in the labor camp, as the active participation of these workers in the changes, that offered new relevant ideas, for example the building of more applicable places to put these electric points, resulting in a better formulation of a round to follow, now located in pertinent position, different than the purposed by the managers.