Why do all rolls have a round hole?

On the steel ruler (tape measure) it turns out there are many features designed to make measurement easier.

You guys are no stranger to rollers - or steel rulers as many people often call right? It is a type of construction made of steel or alloy, capable of being extended by internal springs and mainly used in construction.

However, using a tape measure is not merely a pull-out and measure, because then we can use the normal tape measure as well. On a tape measure there are quite a number of features designed to make measurement easier without us knowing.

The first is the mysterious hole on the head . Each roll has a fold on the top of the ruler, which is used to hook the edge of the table. But that mysterious hole, what do you think it's for?

What is this hole for?

And the answer is here.

This hole is used to hook into a nail cap, in case you have to measure a fairly long section without anyone helping to keep the other end.

Next, notice that the tape end is designed with small serrated grooves . Why not make flat for beauty? That's because when you're done measuring, you'll need something to mark like a pencil. And if there is no pencil, that jagged area will be an extremely effective and fast marker.

Not all. Keep looking at the top of the ruler, you will see that the steel attached to the ruler is somewhat loose. Could it be a design error? No, there's a purpose.

In fact, the first inch and the second inch on the steel ruler are not equal, but are 1/16 inches apart. And you know, that "loose" range is about 1/16 of an inch. That is why we can measure accurately with very few errors.

Finally, look at the back of the case, you will see the "cryptic" numbers as follows.

These numbers are the length of the shell . Usually the left side is in inches, and the right number is in mm. Knowing this number will help you measure objects vertically without suffering as shown below.

How much is this?

Instead, you can confidently measure like this!