The teaching of fractions in elementary school is known to be challenging. Literature indicates that teachers' and prospective teachers' lack of depth of fraction content knowledge and associated pedagogical knowledge is of concern. This study investigated the fraction content knowledge of prospective teachers and their ability to use that knowledge in a novel situation. Prospective teachers who regarded their own fractional content knowledge as weak were recruited to participate in the study. They completed a questionnaire and then participated in a loosely structured teaching experiment in which they were shown how an elastic strip could be used to assist in the development of fraction ideas. Data gained from questionnaires and transcripts of the teaching experiment indicated that using the elastic strip was effective in challenging and enriching the participants' knowledge of equivalent fractions and ordering fractions. The physical nature of the use of the fraction strip required participants to articulate their thoughts to other participants which assisted in making their actions relating to the fraction tasks explicit. The results suggest that the use of the elastic strip, and associated teaching, should be considered as a productive way of assisting prospective teachers to develop their understanding of fractional concepts.