During the industrial design process, a product model undergoes several analyses. One of the most common ones is the finite element analysis. This kind of analysis needs a simplified model, which can include idealised parts, and thus it is usually non-manifold and non-regular. During the idealisation process, the semantic information attached to the CAD model, such as features or surface types, or information used for model simplification, e.g. assumptions on the behavior type, is usually lost, thus making more difficult re-using, or, at least taking advantage, of performed simulations and models. This would be made easier if a meaningful interpretation of the object sub-parts is available. To this aim, in this paper, we provide a taxonomy of form features in non-manifold shapes and we describe an approach for their identification based on a decomposition of a non-manifold shapes into uniformly dimensional components proposed in [DHH06]. The process presented is the first step towards the identification of form features, since it analyzes those features containing non-manifold singularities.