Geometry for Teachers (GeT) courses provide unique opportunities for undergraduate students to hone their proof-writing skills, take ownership of proving, and make connections to secondary teaching. In this talk, we focus on students’ ability to “derive and explain geometric arguments and proofs” (SLO1) – one of the key student learning objectives (SLOs) of a GeT course. We unpack the dual meaning of proof as a process and as a product, and describe different ways in which instructors of GeT courses can support students’ developing proficiency with proof. We also draw connections to other SLOs.