This is one of the best tools I have ever owned. Clicking sound when metal touches metal when closing - The protractor allows angles to be measured - The ridge (where the ruler joins and separates when folded) does not affect the straightness of the line drawn - The hinge tension is loose enough for easy opening and closing, but narrow enough to save angles - measurement markings are engraved and then painted - ruler is small in both height and length (folded) A few additional notes: for people who measure in inches, this will only be in millimeters and centimetres measured; Conversion is an option. Even if the hinge was meant to last a long time, I would carefully open and bend the ruler, just in case. This ruler is well designed and I recommend it to anyone who needs a multi-purpose portable ruler.