Ruler 30cm Staedtler 562 300 Pb Clear First and foremost, rulers are a practical tool for drawing straight lines. To do this, place the ruler at specific points on a drawing or surface. Then trace the edge of the ruler with a pencil or technical pen to draw a straight line on the paper. A ruler can also be used to quickly measure short distances. For a long time, rulers have been part of every primary school students basic supplies. Back in the day when children used to write on slates in school, they needed a cloth to clean their slates. This cloth would hang from a piece of string tied through the hole in the ruler. In this product range, you will find Plexiglas, aluminium and plastic rulers in a variety of lengths for school and office use. Some of these products are non-slip and feature an inking edge, so they are also ideal for technical drawing. Features: Transparent plastic 30cm ruler. With bevelled inking edges. Ideal for students. Scale for left and right handed users. Plastic hangsell sleeve.