A ruler, also known as a rule, is a flat, straightedge measuring instrument with equally marked spacing etched or moulded along its length. The spacing forms a measuring scale of either metric or imperial measurements, which are usually in increments of centimetres (cm) and millimetres (mm) and inches (sometimes denoted as ") respectively. Rulers are used to measure the length of an object or its edge precisely and as a guide for drawing or scoring straight lines. Some rulers have measurements on both sides. The edges of rulers are often bevelled to reduce measurement errors.

Who uses rulers?

The better question may be 'who doesn't?' Rulers are used everywhere, from schools and offices to within the home and in a wide range of occupations. They are prevalent is particular fields of study including geometry, printing, technical drawing, architecture, building and engineering.

What are the different types of ruler?

Rulers are made from durable materials like wood, plastic or metal. These materials are hard wearing and are usually shatter resistant and scratch proof as they are made to last a long time.

• Transparent plastic rulers allow an unobstructed view of the surface underneath for precise measuring and drawing.
• Stainless steel rulers or an aluminium ruler is very durable and are ideal for use in a workshop. These steel rules often have a satin chrome anti-glare finish for clear visibility of the scale.
• Wooden rulers are ideal for use at home or in schools, as the wood has a smooth surface, is clear to read and won't split.
• Flexible rulers or tape measures, are ideal for determining the dimensions of objects with curves and angles. They are able to bend and flex to measure an exact circumference, length, width or height.
• Machinist's rulers are made from steel and are usually a 6 inch ruler. The imperial machinist scale ruler is divided into increments of 1/10 inch. The metric machinist ruler is divided into millimetres or half-millimetre increments, allowing small, precise measurements to be taken with accuracy.