In this article, the authors share their favorite "Construct It!" activity, which focuses on rate of change and functions. The initial approach to instruction was procedural in nature and focused on making use of formulas. Specifically, after modeling how to find the slope of the line given two points and use it to solve for the y-intercept, the authors gave students time to practice. They recognized that their approach lacked an opportunity for students to engage in reasoning and sense making. According to Lithner (2008), imitative reasoning (i.e., a focus on memorizing) is ubiquitous in mathematics classrooms in the United States, whereas creative reasoning (i.e., reasoning that results in knowledge creation) is rare. To help students generalize the process of identifying a linear relationship that holds for two ordered pairs, explain the connection to the slope formula, and engage in creative reasoning, the authors designed the activity they call Turn A Into B. This activity focuses on reasoning about the relationship between two quantities and reflecting on how this is related to rate of change and functions.