National FAQ: What is a linear measuring device (the rules are vague)? (section: 3 / paragraph: l / sub-paragraph: / line: 1)
A: A linear measuring device is any item marked are regular, standard intervals suitable for measuring length. It must have markings in only one dimension (ruler, meter stick, tape measure, caliper, etc). A carpenter's square would not qualify as it has markings along two dimensions.
National FAQ: Is a T-square considered a linear measuring device? (section: 2 / paragraph: c / sub-paragraph: / line: 1)
A: As long as it has regular markings along only one axis of the t-square, yes, it would be considered a linear measuring device. A carpenter square or framing square is marked along two axes and would not be allowed.