Understanding is one of the four key proficiencies in the "Australian Curriculum: Mathematics" and arguably the pivot on which mathematics depends. This case study investigated preservice teachers' understanding and ability to articulate some measurement concepts. Data were gathered from 23 preservice teachers who voluntarily participated in a series of learning sessions focused on literacy in mathematics. The study highlights potential difficulties that preservice teachers have with some mathematical concepts. The paper argues that understanding of concepts and an ability to articulate them well are keys to teachers being able to aid their upper primary and middle years' students build a solid foundation of mathematical ideas.