This article focuses on the trajectories, knowledge and circulation of “suitcase traders” in a trans-border city between Mongolia and China. Widely feminine, this trade nourishes the major part of open markets in Central and Northeast Asia. The paper analyzes the Mongolian traders’ circulatory paths, which transform the twin cities of Erlian-Zamyn üüd into a kind of caravanserai. The suitcase trade in this trans-border city requires skills for building social networks and know-how in order to circulate. The Mongols associate these skills with their traditional pastoral nomadic lifestyle.