Tangible User Interfaces (TUIs) have drawn the interest of HCI and learning communities because of their potential positive impact on the learning experience. In this paper, we describe a preliminary study of a TUI application for training spatial skills of carpenter apprentices. We designed a tangible interface to perform a CAD modelling activity in a way that resembles what apprentices do in the workspace: shaping a wooden brick through sequential cuts by using a saw. The core of the study is to compare the effects of TUI and GUI on the user experience, by taking advantage of eye-tracking data. We report two main findings: first, the successful employment of eye-gaze tool in TUI research which represents a novelty per-se. Second, a significant impact of the TUI on the user experience which gives some insights about the cognitive benefit of tangibles.