What tool is used to measure length and can be easily folded for storage?

The correct choice is a folding rule, which is specifically designed to measure length while being easily foldable for convenient storage. Folding rules typically consist of several hinged sections that can be opened out to measure longer distances while collapsing into a compact form for easy transport and storage. This attribute makes them particularly practical for carpenters, builders, and other tradespeople who need to carry measuring tools on the job site.

In contrast, a rigid steel rule is typically a straight, flat piece of metal or plastic that cannot be folded and, while it provides accurate measurements, it occupies more space and is less portable than a folding rule. A tape rule, while flexible and portable, does not fold in the same manner as a folding rule; it usually retracts into a housing for storage. Calipers, on the other hand, are tools used to measure the distance between two opposite sides of an object with high precision but are not designed for general length measurement of longer distances and do not have a folding capability.