folding rule

One of the most rare finds is the 350-year-old folding rule discovered on an unidentified underwater site.

Must carry folding rule in hip pocket.

An ordinary foot rule, or a folding rule, will give results sufficiently accurate for the water prospector in this instance.

He took a thin folding rule of aluminum from a waistcoat pocket, and applied it to the most clearly defined of the three footprints.

The inspector took a folding rule from his pocket and with it pointed out the traces.