On any tester platform, most production test programs require resource sharing for the best cost-of-test. To improve test economics, a higher site count is desired, which demands more instruments in the test head, unless resource sharing is applied to better utilize the existing configuration. However, thorough resource utilization planning is mandatory to avoid making mistakes when developing the test concept block diagram. With medium to high pin count devices, this can become a tedious and time-consuming task, especially when using many sharing elements like multiplexers, matrices and relays. To keep the overview about which resource is required on which device pin at what point in time, a bulletproof method is required to identify the sharing opportunities while preventing resource conflicts. This presentation outlines a simple step-by-step process starting from test specification to an optimized solution using a table called Resource Utilization Grid (a.k.a. the RUG) to balance resource usage and instrument sharing along the test flow to achieve highest site counts on the ETS-800 utilizing its innovative APEx architecture.