The concept of specificity of enzyme action can potentially be abstract for some students as they fail to appreciate how the three-dimensional configuration of enzymes and the active sites confer perfect fit for specific substrates. In science text books, the specificity of enzyme-substrate binding is typically likened to the action of a lock and key whereby only one specific key can open a lock. However, there are some inherent limitations to this analogy--the lock represents the enzyme but it is the one that is changed during the interaction (it will open) rather than the key, which represents the substrate (remains unchanged). Further, the lock and key hypothesis is limited in its ability in helping students understand the random nature of particle collision between enzymes and substrates. To help students learn (1) the specificity of substrate binding to the active site of enzymes, and (2) the random collision of enzyme and substrate molecules to sample for a complementary pair, we designed a series of models using three-dimensional printers to provide students with a concrete touch and feel of three-dimensional configuration to enable students to visualise the abstract concept of specificity. To augment students' understanding after working with the three-dimensional models, an animation about enzyme action was developed. The models and the animation serve as resources to enhance students' understanding of enzyme action.