Investigating the field of engineering offers the opportunity for interdisciplinary, hands-on, inquiry-based units that integrate real-world applications. However, many K-12 students are not exposed to engineering until they enter college. Get a Grip! is a problem-based unit that places middle school students in the role of engineers who are challenged to design and construct prosthetic arms for amputees in a war-torn country. The students use common materials to build arms that accomplish tasks requiring fine motor control and strength. A critical component of the unit is its ability to demonstrate to middle school students that strong, interdisciplinary knowledge is required to solve engineering problems. As such, it is a practical and efficient mode of interdisciplinary instruction meeting state and national standards in science, math, reading, and social studies. This article discusses the structure of Get a Grip! (Contains 2 figures and 1 online resource.)