A lintel is the horizontal beam or stone placed across the top of a doorway, window, or other opening in a wall. The lintel's job is to support the weight of the wall above the opening, keeping it from collapsing inward.

If you've ever stacked blocks or books to make a little fort, you know that leaving a gap for a door creates a problem: what holds up everything above it? That's exactly what a lintel does in real buildings. Ancient builders discovered that placing a strong piece of wood or a thick stone across the top of an opening would carry the weight safely around it.

You can spot lintels above almost every door and window. In old stone buildings, the lintel is often clearly visible as a thick rectangular stone stretching from one side of the opening to the other. Some of the world's oldest standing structures, like Stonehenge, use massive stone lintels resting on top of vertical stones.

In modern construction, lintels might be made of steel, concrete, or specially engineered wood, but the principle remains the same: this crucial piece bridges the gap and carries the load. Without lintels, builders would need to use arches over every opening, which is much more complicated.