We define, classify and discover new functions, aspects and types of marking as a body skill. Through a cognitive ethnography of a top class dance company we collected extensive video data on the complete rehearsal process as well as concise speech extracted from multiple interviews made to the dancers and the choreographer. We provide a detailed qualitative explanation of the dancers’ activity to show how marking can be a vehicle for physical thinking. The dancers’ bodies perform multiple cognitive functions when marking. Dancers mark for recall, but also for refining, communicating and coordinating new relevant multimodal information during the rehearsal of a new choreography. Moreover, a quantification of the sequence of movements and the definition of invariant geometrical transformations provides an objective account of this interactive phenomenon.