ELI5: Explain Like I'm 5

Nail (unit)

A nail is a little piece of metal with a pointy end that people use to hold things together. You know how when you're trying to build a fort out of pillows and blankets, you can use a clothespin to hold them together? A nail is like a super-strong, permanent clothespin.

When people talk about nails, they usually mean how long they are. Nails come in different sizes, from teeny-tiny little ones that are only a few millimeters long, to really big ones that can be several inches long. They also come in different thicknesses, which is called the gauge.

The most common type of nail that people use is made of steel. It's shaped like a little stick with a pointy end and a flat top. When you want to use a nail to hold two things together, you start by making a hole in one of the things you want to attach, then you stick the pointy end of the nail through that hole and hit the flat top with a hammer. This drives the nail into the other thing and holds everything together.

There are different types of nails for different jobs. Some nails have special shapes, like a horseshoe, that are designed for specific uses. Others are made of different materials, like copper or brass, and are used for decorative purposes.

Overall, nails are a really important part of building things, from houses to furniture to toys, and they come in all sorts of shapes and sizes to make sure everything stays together securely.