Answer:
Kiln-baked bricks
Explanation:
The mud brick was put in the sun and allowed to be dried in the sun. The hotter the sun, the stronger the brick would be. Oven-baked bricks were made by the same process. When the bricks were dried throughout, they were stacked in ovens called kilns, which were heated by fire. But the sun wasn't always out and you couldn't always make bricks on days without sun. Ovens were available whether it rained or didn't.