is a geometric tool that can be used for measuring distances or drawing . Rulers are typically made of plastic, wood, or steel, but other materials may also be used.
To use a ruler to measure a distance, one or more length scales are printed on the ruler. Rulers come in various sizes, lengths, and shapes. Many rulers come in the shape of a , usually with a length 3 to 15 times greater than its width. The ruler depicted below has a length 7 times greater than its width.
When a ruler is used for measuring a distance between two , the ruler is placed with its edge intersecting both points. For many measurements, the ruler can be placed so that the edge intersects one of the points at the measure 0
on the ruler. The distance can then be read directly on the measuring scale.
Sometimes, due to physical restrictions, it may be impossible to measure from 0 on the ruler. In such cases, the difference between two measures on the ruler can be calculated to find the distance between the points.
A ruler can be used as a to draw a segment between two points. The ruler is laid with its edge intersecting both points and the segment is drawn by running a pen or a pencil along the edge of the ruler.