As augmented reality (AR) systems proliferate and the technology gets smaller and less intrusive, we imagine a future where many AR users will interact in the same physical locations (e.g., in shared work places and public spaces). While previous research has explored AR collaboration in these spaces, our focus is on co-located but independent work. In this paper, we explore co-located AR user behavior and investigate techniques for promoting awareness of personal workspace boundaries. Specifically, we compare three techniques: showing all virtual content, visualizing bounding box outlines of content, and a self-defined workspace boundary. The findings suggest that a self-defined boundary led to significantly more personal workspace encroachments.