In this study, we examined the ability of grades 1-8 pre-service teachers (PSTs) to engage in thinking about patterns, relationships, and functional rules. Using the algebraic habit of mind Building Rules to Represent Functions as a framework, we examined whether and how well our PSTs (n = 18) used seven features of this habit of mind: organize information, predict patterns, chunk information, use different representations, describe a rule, describe change, and justify a rule. The data revealed distinct and significant differences among our PSTs' demonstrated abilities to justify a rule, organize information, predict a pattern, and describe a rule. Their ability to justify a rule was the weakest of the seven features, and it was correlated with the ability to predict patterns and the ability to chunk information. Our analysis reveals the complexity of the relationships among the seven features and provides a tentative grouping of features that together might support one another. Attention to these relationships has the potential to enhance instruction aimed at helping students learn to analyse problem situations that focus on writing rules to represent functional relationships.