Using cultural-historical activity theory as my framework, I report an empirical study of how electrician apprentices learn to bend electrical conduits in college and on the job. The requirements for doing well in the two locations are very different: exhibiting knowledge of trigonometry, on the one hand, and doing a good job that makes bending and subsequent pulling of wires practical. Formal trigonometry is the reference in the classroom, whereas rules of practice are the main references on the job. In each case, the practices orient themselves to the Canadian codebook, which provides a description that the inspector uses as his/her reference when checking for approval. However, the sharp differences between the two forms of practice and the contradictions arising from them are reintegrated into the stories that are constitutive of the community of practice. Implications are discussed with respect to the concept of "boundary crossing" through the lens of cultural-historical activity theory and its concepts for the development of the individual: subjectification, which describes the changes within an activity system (school, work) and personality, the changes the individual undergoes as he/she moves repeatedly between systems of activity.