This article describes a valuable lesson that university mathematics faculty members learned from fifth grade and middle school teachers in a professional development workshop. The goal of the workshop was to show how models for whole number operations could be linked to models for rational numbers and to connect the traditional algorithms to the models. While working problems, most of the teachers modeled multiplication of whole numbers, fractions, and decimals using the newly taught area model. Several presented an area model for decimals in an unanticipated way that led to an incorrect answer. The lesson learned was that to attain correct products from models, consistency in setting up the factors in an area model for multiplication is needed as the factors change from whole numbers to fractions and decimals. In the case of using base-10 blocks to represent the factors, the name of the block must be the same as the upper surface area of the block so that correct answers can be interpreted when modeling multiplication of whole numbers and decimals.