Red clay roof tiles appear in many architectural traditions around the world, despite the cultures being geographically or historically distant. However, this isn't necessarily surprising. Clay is an abundant and accessible building material worldwide, with some studies and other sources suggesting it comprises approximately 10-13% of the Earth's soils. Red tiles, in particular, are often a product of the local soil's mineral content and the firing process. Their widespread use across unrelated regions is less about shared cultural influence and more about material logic: clay is cheap, durable, and easy to work with using simple tools and techniques. In Vietnam, for example, there is a unique and visible tradition of clay tile use that dates back centuries. Regions like Vinh Long, nicknamed the "kingdom of red ceramics", have an abundance of this material, supporting a long history of tile-making. In some parts of Vietnam, these tiles are known as Yin-Yang tiles, due to the concave and convex shape in which they are formed during production.