The reuse of previous design knowledge when tackling a current problem is a potentially important way to improve design efficiency. However, unguided reuse is fraught with problems. Our current goal is to try and limit the problems associated with reuse in engineering contexts by means of a computer-based support tool which guides the effective encoding of information for subsequent reuse. This paper presents an evaluation of such a tool that we have developed, which is known as Desperado. The evaluation involved observing academic designers working on a short design brief, either with or without Desperado. Our observational data are reported in conjunction with designers' subjective experiences of using Desperado. It was found that whilst the introduction of the system changed the nature of the users' design work, these changes were primarily associated with a better exploration and evaluation of possible design options.