The University of Denver's Penrose Library's Stacks Maintenance unit is a separately managed unit that works in collaboration with all library departments to ensure complete access to the library's print collections. This unit takes advantage of a variety of techniques and tools to fulfill its mission, including a fine-tuned tracer system for identifying and locating missing, lost, and claimed-returned books. This article discusses the successes of the collaboration between the Stacks Maintenance unit and the other departments in Penrose Library to improve service in the confounding area of inventory management, specifically as it relates to inventory flow and lost or missing books. Missing books are a costly issue both from a fiscal and from a service standpoint. To address this issue, we have tailored a plan to identify missing books, to efficiently and effectively search for these materials, and finally, to maintain the stacks in a manner that decreases both the quantity of books unavailable and the length of time books are unavailable to our patrons. (Contains 1 note.)