Specialist plain rule used in correcting or annotating legal papers has dimensions suitable for forming standard correction margins

摘要

The rectangular rule is 7 cm wide, in accordance with the required edge correction width, and 30 cm long, based on a DIN A4 sheet length of 29.7 cm. It carries no scales, since it is not used for measurement, merely to define the margin. Other conventional (i.e. scaled) rules with the same width are also claimed, since they could be used for the same specialized purpose.