This paper presents the application and evaluation by means of a controlled experiment of an instructional tool during an Open and Distance Learning (ODL) course. The core issue of investigation is whether this instructional aid can support, guide and scaffold the distant student in his/her study. For this purpose, a controlled experiment was conducted with the participation of 191 undergraduate students. Descriptive statistics as well as a variety of statistical methods have been applied to the collected data, in order to test the research hypotheses. The results have shown a statistical significant difference in performance for the student group that used the tool. Finally, concerns about the application of the tool in a broader context and further research on the area are also presented.