Scale, sometimes called scale or line gauge, is a kind of equipment used to calibrate straight line in geometry, technical drawing, engineering and architecture. The equipment used by the Engineer (before CAD) will mark the scale (scale) on its edge when marking or measuring the length on the drawing. Instead of using scale bars to draw lines, they used set or T squares to draw lines.

For a long time, rulers are made of different materials and have a wide range of dimensions. Some are made of wood. Since its invention, plastics have also been used. They can be molded with a length mark instead of being crossed. Metal is used for more durable rulers in the workshop; sometimes the metal edge is embedded in a wooden ruler to retain the edge when used for straight cutting. A 12 inch or 30 cm ruler can be placed on a table to help with drawing. The shorter scale is easy to put in the pocket. In some cases, a longer ruler is required, such as 18 inches (46 cm). Also use a yard long rigid wooden or plastic yardstick and a meter long meter rule. Traditionally, the longer measuring rod is used for larger projects, and now it has been replaced by tape measure or laser rangefinder.

The table ruler is mainly used for three purposes: measuring, helping to draw lines, and as a linear guide for cutting and scoring blades. The edge of the actual ruler is marked with a distance.

Wire gauge is a ruler used in the printing industry. These can be made of a variety of materials, usually metal or transparent plastic. The unit of measurement on a basic gauge usually includes inches, agates, 12 point type, and points. More detailed wire gauge may include sample width of line, common type samples of several point sizes, etc.

When not in use, a measuring instrument that functions like a ruler can be portable by folding (carpenter's folding ruler) or retracting a coil (metal tape). When extended, they are as straight as a ruler. The illustration on this page shows a 2 m (6 ft 7 in) carpenter's ruler that can be folded to 25 cm (10 in) in length for easy pocket placement, and a 5 m (16 ft) tape that can be retracted into a small house.