Design activities typically involve and culminate in the creation of models representative of new ideas and conceptions. The format is often dictated by the specific discipline, with ideas in design and technology education regularly being externalised through the use of computer aided design (CAD). This paper focusses on the realisation stage of a design process, specifically when conceptual ideas are being externalised through CAD. Acknowledging students as novices or quasi-experts with regards to their levels of technical expertise and recognising the limitations in the cognitive capacities of humans suggests merit in investigating problem solving strategies through the lens of heuristics. A comparative study was employed between two distinct CAD systems to examine students modelling behaviour. Considering the situational context of the problems encountered and the bounded rationality which the students are operating within, a number of insights are generated from the findings which are of importance from a pedagogical perspective within design and technology education.