Diagrammatic activity and communicating about it in different representational systems is essential for mathematical discourse. Therefore, it is also of great importance for individual mathematical support. So far, little is known about how teachers conduct such discourses with children. By analyzing the diagrammatic activities and the communication about them with an analyzing method developed for this purpose, patterns of diagrammatic activity and communicating about it can be elaborated. The example of an individual learning support between a preservice teacher and a second grade student who work in the representational systems of natural numbers and the field of twenty is presented. It shows that these patterns can be supportive in dealing with errors.