You would then slide the ruler's inner section all the way out to the right. That section has the last 2 cm of the ruler on its right-hand end, leaving the main body of the ruler 10 cm long.

Rollbe’s super compact versions – 4 Inch and 10 cm are designed to be the most compact ruler on the market. They are similar to the size of a coin, so the ruler will always fit in your pocket.