Focusing on the analysis of the rent strike in the French Sonacotra hostels for immigrant workers between 1973 and 1981, this article aims at unearthing the genesis, in a particular historical context, of a social movement consisting of immigrants whose legal status is by definition precarious. The study of the biographical itineraries of social movement leaders and supporter activists enables to highlight the complex process of production and reconversion of specific militant capitals. In addition, the analysis stresses the need to take into account the external support which is an essential part of any mobilisation deemed to be unlikely. Finally, the socio-historical inquiry shows the means by which the deprived social agents attempt to subvert the institution by which their practices are bound in order to air their grievances.