When mathematics teachers plan lessons, they interact with curriculum materials in various ways. In this paper, we draw on Brown's (2009) "Design Capacity for Enactment" framework to explore the practice of "adapting" curriculum materials in the case of a Singapore secondary mathematics teacher. Problems from the textbook used and the worksheets she crafted were compared to determine how she adapted the content. Video-recordings of the lessons and post-lesson interviews were used to clarify how her personal "teacher resources" contributed to her design decisions. The findings suggest that her seemingly casual use of problems from the textbook are in fact unique variations of adapting curriculum materials.