The same features, when denoted by reference signs, must, throughout the application, be denoted by the same signs.[Rule 46(2)(i); ]

There would be considerable confusion if a single feature were allocated different reference signs in the various drawings. However, where several variants of an invention are described, each with reference to a particular figure, and where each variant contains features whose function is the same or basically the same, the features may, if this is indicated in the description, be identified by reference numbers made up of the number of the figure to which it relates followed by the number of the feature, which is the same for all variants, so that a single number is formed, e.g. the common feature "15" would be indicated by "115" in Fig. 1 while the corresponding feature would be indicated by "215" in Fig. 2. This system has the advantage that an individual feature and the figure on which it is to be considered can be indicated at the same time. It can also make complex cases involving many pages of drawings easier to read. Instead of the common reference sign being prefixed by the number of a figure, it may, when the individual variants are described with reference to particular groups of figures, be prefixed by the number of the particular variant to which it relates; this should be explained in the description.