What’s inside a tape measure?

It’s useful for measuring, fun to extend out as far as possible, and when its rocker is unlocked, the long metal measuring blade snaps quickly back inside of its shell. But how? What’s inside a tape measure?

In this clip from the Science Channel’s Machines: How They Work, the humble tape measure’s engineering is revealed. We also visit a factory in the United Kingdom to see how the metal is cut, painted, printed, and coiled.

Next: More engineering, more measuring, and why the metric system matters. Plus, What’s on the inside of a fishing reel? And how does a retractable ballpoint click pen work?