Keith Borer Consultants employs physical fit experts that can determine whether two items, recovered separately, originated from the same source - in the way in which two pieces of a jigsaw fit together - or perhaps just share class characteristics typical of a particular manufacturing process but which are not individually discriminating. In many cases, this evaluation can be of significance. Most commonly we are asked to look at drugs wraps of foil or cling film or broken implements, pieces of glass or wood. We can compare these microscopically or using polarising light to establish if there are common features which correspond, for example, on their fracture surfaces or in manufacturer’s defects or features.