The requirements relating to the form and content of drawings are set down in Rule 46. Most of these are formal (see A-X), but the examiner may sometimes need to consider the requirements of Rule 46(2)(f), (h), (i) and (j). Of these, the only question likely to cause difficulty is whether the textual matter included on the drawings is absolutely indispensable. In the case of circuit diagrams, block schematics and flow sheets, identifying catchwords for functional integers of complex systems (e.g. "magnetic core store", "speed integrator") may be regarded as indispensable from a practical point of view if they are necessary to enable a diagram to be interpreted rapidly and clearly.