The design of the instrument support system for the Daniel K. Inouye Solar Telescope (DKIST), located at the Haleakala Observatory on Maui, presented several challenges. These challenges included the need to be able to reconfigure instruments in the future, a highly complex opto-mechanical layout that did not conveniently align with the underlying structure, seismically driven mechanical resonance requirements, and formidable site handling and transport logistics. These challenges were overcome using a modular design that combines 0.5-inch steel plates, W6X25 support beams, and a flexible clamping system to fasten the system to the underlying structure. This design relied largely on an iterative, finiteelement structural analysis that guided modifications and provided the fast turnaround times needed to meet tight project deadlines. The analysis revealed a need to increase the size of the instrument support beams and reinforce them with weldments to increase torsional rigidity. Creating a stiffer, more uniform support structure with larger, reinforced beams not only resulted in a structurally sound architecture but it also simplified the installation process. This paper summarizes the requirements, design, development, analysis, fabrication, and installation of the DKIST’s instrument support structure, known as the “coudé rotator interface–mechanical,” or “CRIM.” The design effort began in September 2016 and the installation of the CRIM was completed in late February 2018, ahead of schedule and with greaterthan-expected accuracy.