Tape measure

Tape measures are portable measuring devices. Several styles exist, having in common a flexible or semi-flexible blade (the tape) on which distances are marked. Many styles also feature a spool for winding the blade (which may be spring-loaded and self-retracting), and a case for protecting the blade and spool.

Flexible vs semi-flexible blades
Semi-flexible blades are typically steel, and curved in cross section. This design enables them to stay straight for several feet, even if they are unsupported, but prevents the blade from adapting to curved or uneven surfaces. They are useful in work such as carpentry and iron working, where long, straight distances must be measured. Semi-flexible tapes may have tables or other information on their reverse side, but typically only have measurements on one face.

Flexible tapes are often fabric or flexible plastic, and while they cannot stand unsupported, they can follow uneven surfaces. These tapes are useful where following an uneven surface is important, such as sizing clothing to a person's body. Since flexible tapes are flat, both faces of the tape can be used for measuring. Some designs feature metric on one face and SAE on the other; other designs use one face of the tape to measure from one end of the tape, and the other face to measure from the other end of the tape.