This document summarizes a presentation about developing number sense in students. It discusses clothesline math, an instructional tool using an open number line to build understanding of numbers and their relationships. It also defines number sense as a flexibility and automaticity with numbers, and the ability to choose strategies and judge answers. The presentation advocates for instructional routines to focus learning on mathematical practices and make lessons accessible for all. Attendees then planned clothesline math activities considering number choices, strategies, and questioning.