This paper reports on the different gesture types employed by twenty-three Year 10 students as they endeavoured to explain their understanding of rate of change associated with the functions resulting from two different computer simulations. These gestures also have application to revealing students' understanding of functions. However, interpretation of gesture is problematic but classification of gestures assisted in the analysis of the video-recorded interviews probing participants' conceptions of rate of change. This paper builds on the classifications reported in previous research. Five additional gesture types are presented, which provide insights into students' thinking about rate of change, and hence functions. [This study is part of the RITEMATHS project.]