What is a folding rule?

Uses

Measurement

Folding rules can be used for measuring both small spaces and longer distances. They can be transported easily once they are folded up, making them useful when working in the field.

Angles

Folding rules can also be used to help determine angles on larger structures or for places which are difficult to measure with a just protractor. Sections of the rule can be lined up with an angle, the angles of the rule can then be measured with a protractor.

For more information see:  How to measure angles with a folding rule

Parallel lines

Folding rules with more than two rule strips can be folded in such a way that it can be used to quickly draw parallel lines down a surface with a straight edge. These rules can be folded into a the shape of a ‘4’ held upside down with two rule strips at right angles to each other. One rule will line up with the edge of the surface and it can be moved up and down to draw parallel lines.

Special marks

Some folding rules come with specialist markings, for different uses. For example, masonry folding rules have markings on one side to show the proper dimensions of the bricks and mortar joints needed to lay a structure of a specific height or length. Surveyor’s folding rules are distinctly marked out every 10th of a foot or metre.

Folding rule or tape measure?

The tape measure has replaced the folding rule for many uses. However, the latter still maintains its position for some purposes, such as construction, where rigid long measuring instruments may be preferred over flexible ones.

Advantages and disadvantages of folding rules

• Folding rules are rigid once locked into place, forming a straight measuring instrument
• They can be placed so the gradation marks are flat against a surface, allowing for accurate measurements
• When folded down to a smaller size, they can be used in just one hand
• They can be used, along with a protractor, to measure angles

• Folding rules are not suitable for measuring curves or circles
• Over time the hinges can come loose, which will make them lose accuracy as the measurements will change
• Wooden rules can change shape if they are exposed to moisture for a long time, making them inaccurate. Some plastic rules can be easily damaged along their straight edge. Steel rules may rust

Advantages and disadvantages of tape measures

• Tape measures are available in longer sizes than folding rules
• The flexible tape can be used to measure curves and circles, as well as straight lines
• The plastics, steels or fabric tapes are made from are resistant to rust
• The tape can usually be locked into place at any length, up to its maximum
• Most tape measures have a hooked end to grip the edge of a surface

• The flexible tapes may not be as accurate for measuring straight lines as a folding rule. There is more chance of them moving when being read
• You usually need both hands to take measurements with a tape measure, and sometimes you’ll need a second person. Modern spring tapes will spring back into the casing if not held or locked into place
• The shape of the tape in spring measures makes it difficult to lie the tape flat against a surface, making readings less accurate
• If the hook at the end of a tape measure is damaged it will affect its accuracy