Why is this the answer?

The answer is nail because this is a very clever little riddle that makes you think about an object we use every day to build and fix things. A nail is a small, hard piece of metal with two very important parts. One end has a sharp point, and the other end has a flat, wider part. That flat, wide part is always called the "head" of the nail. When a builder or a carpenter wants to put two pieces of wood together, they use a hammer to drive the nail into the wood. They hit the head of the nail with the hammer, pushing the long, pointy part down, down, down into the material. The long, main section of the nail is what goes deep into the wood or wall. This is exactly what the riddle means by "I hide." The nail's body, which is also called the shank, is tucked away safely inside the wall or the board, and you can no longer see it. It is completely hidden from view and is doing the essential job of holding everything tightly in place. However, the person pounding the nail cannot let the whole thing disappear! They need a flat place for the hammer to strike, and they need a way for the nail to stop sinking into the wood. That is why the very top part, the flat "head" of the nail, always stays sticking out. This "head" is left on the outside, resting right on top of the wood or the wall. It is the one part of the nail that is still visible once it has been fully used. The head is outside, while the rest of the nail is hiding inside the wood, exactly as the riddle says. The nail is a perfect answer because it fits both clues so well. It is a simple, hardworking tool with a special way of working. Its long body hides to connect pieces of material, and its head stays outside as a marker and a stopping point. The riddle uses fun language to describe the nail's parts as if they were a person playing hide and seek. It is a wonderful example of how riddles turn very ordinary objects into a tricky, smart puzzle for us to solve.