Proper resource allocation at Border Patrol checkpoints is essential for effective and efficient screening. Improper resource allocation can lead to flushing-i.e., allowing cars to pass through a checkpoint without screening-or cost inefficiencies. To better inform resource allocation, we present a prototype simulation that models the major processes of an operational checkpoint. Data for the simulation was collected during extensive site visits to checkpoints on the U.S. northern and southern borders. In a case study, we configure the simulation to model the Tucson Sector, I-19 checkpoint. We found that the checkpoint can handle current traffic demands, but additional screening capacity is needed to accommodate traffic in the next 20 years.