Our observations of landscape architecture students revealed a new phenomenon-interstices. Their bimanual interactions with a pen and touch surface involved various sustained hand gestures, interleaved between their regular commands. Positioning of the non-preferred hand indicates anticipated actions, including: sustained hovering near the surface; pulled back but still floating above the surface; and resting in their laps. We ran a second study with 14 landscape architect students which confirmed our observations, and uncovered a new interstice i.e. stabilizing the preferred hand while handwriting. We conclude with directions for future research and challenges for designers and researchers.