During abutment tooth preparation for fixed partial dentures, the presence of undesirable undercuts, due to clinical complicating factors such as poor visibility and access, frequently is observed.1 The presence of undercuts may hinder the complete seating of the cast restoration, resulting in the need to recontour the prepared tooth and make a new impression. This article presents an easy and quick method for evaluating single or multiple tooth preparations to detect undercuts before making the final impression.