Research indicates that understanding levels of abstraction (LOA) and being able to move between the levels is essential to programming success. For K-5 contexts we rename the LOA levels: problem, design, code and running the code. In our qualitative exploratory study, we interviewed five K-5 teachers on their uses of LOA, particularly the design level, in teaching programming and other subjects. Using PCK elements to analyse responses we found our teachers used design as an instructional strategy and for assessment. Our teachers used design as an aide memoire and the expert teachers used design: as a contract for pair-programming; to work out what they needed to teach; for learners to annotate with code snippets (to transition across LOA); for learners to self-assess and to assess 'do-ability'. Teachers used planning in teaching writing to scaffold learning and promote self-regulation revealing their understanding of student understanding. One issue was of our teachers' knowledge of terms including algorithm and code; we propose a concept of "emergent algorithms". Our findings suggest design helps learners learn to program in the same way that planning helps learners learn to write and that LOA, particularly the design level, may provide an accessible exemplar of abstraction in action. Further work is needed to verify whether our results are generalisable more widely.