Teachers and teacher educators have been sharing strategies and resources for implementing mathematics routines in National Council of Teachers of Mathematics (NCTM) journals for years. A less commonly shared mathematics routine, especially with young learners, is "Clothesline Math" (Shore, 2017, 2018). In this routine, teachers create student opportunities to integrate spatial reasoning with other concepts by sequencing mathematical representations on life- size number paths (Marcella- Burdett et al., 2020). Students hang number tents made from index cards or printed from Internet sources on one or more clotheslines. Clothesline Math allows multiple entry points as Pre- K--3 students move along developmental trajectories for counting, subitizing, comparing numbers, and adding/ subtracting (Clements & Sarama, 2017/2019). As students move tents showing mixed groupings of quantity (Figure 3; Acosta, 2021), they are relying on more than memorized counting strategies. Consequently, students have opportunities to subitize conceptually instead of just perceptually (Sarama & Clements, 2009) to support the construction of arithmetic units (Wilkins et al., 2022).