Crew quarters (CQ) design was key to the habitability design of Skylab, with a specific goal of providing a private space for each crewmember, who might spend 6-8 hours a day there. Despite the privacy afforded by a designated place for each crewmember, Skylab crews reported poor sleep due to noise, light leaks, or disturbances by fellow crewmembers. Adams (1998) noted that Skylab lacked attachment points for relocating sleep restraints, thereby effectively precluding crewmembers from sleeping elsewhere. Generally speaking, Skylab's interior outfitting was not designed for modularity or reconfigurability. In contrast, one of the principal design features of the International Space Station (ISS) is the basic structure of the modules and the rack volumes they accommodate, the International Standard Payload Rack (ISPR). The ISPR is intended to allow interchangeability and reconfiguration. Feedback from expedition crews who have lived onboard the ISS include requests for an improved living environment. Designers can improve the living environment, in part, by learning from the experiences of these crews. By developing solutions that can be retrofitted to the existing basic structures, designers could offer an environment that enriches a crewmember's experience. Crew feedback has cited flexibility of use as a desirable feature during long-duration missions. For such missions, flexibility allows objects or environments to be used in different ways, requiring fewer amenities and less room to house those amenities, thereby reducing transportation demands and costs. Flexibility offers numerous advantages for space applications where the living volume is limited and delivery and maintenance costs are major concerns. A mounting structure and kit of parts system could offer flexibility of use, a benefit for crewmembers who desire visual stimulation and variety in the space station environment. Moreover, this approach is durable; any part would be able to be detached and updated, improved, or replaced. This chapter presents a design solution for a flexible CQ system. The process behind the solution involved a series of self-directed empirical exercises that provided insight and spurred concept generation. Subsequently, a review of relevant ISS specifications served to guide design development. The resulting design is compatible with the basic elements of existing CQ equipment, offers adaptability over time using a proposed kit of parts, and thus an interior strategy that allows crewmembers to tailor the layout and use of their private environment at any time.