Spatial thinking is important for success in engineering. However, little is known about "how" students learn and apply spatial skills, particularly in kindergarten to Grade 12 engineering learning. The present study investigated the role of spatial thinking in engineering learning at a middle school summer camp. Participants were 26 students (13 female, 13 male), predominantly from underrepresented groups. We took a cognitive ethnographic approach, using observations of hands-on engineering learning activities to identify moments when spatial problems arose and how learners made sense of these problems. We describe these processes as "distributed spatial sensemaking" because they involved both internal (cognitive) processes and also interactions with other learners, materials, and representations. We identified 90 distributed spatial sensemaking episodes in our data set. These episodes facilitated important engineering practices such as hypothesis testing and design iteration. We also found that different activities elicited different types of distributed spatial sensemaking episodes. Our results demonstrate how spatial thinking matters in everyday engineering learning and speaks to the types of engineering learning activities that scaffold particular spatial processes and practices. Our research also shows how cognitive, situated, and distributed theories can be used in tandem to make sense of a complex phenomenon like engineering learning.