The procedure by which humans identify checks in check positions is not well understood. We report here our experience in modelling this process with CHREST, a general-purpose cognitive model that has previously successfully captured a variety of attention- and perception-related phenomena. We have attempted to reproduce the results of an experiment investigating the ability of humans to determine checks in simple chess positions. We propose a specific model of how humans perform this experiment, and show that, given certain reasonable assumptions, CHREST can follow this model to create a good reproduction of the data.