What is one of the main purposes of a door sill?

One of the main purposes of a door sill is to drain off water. A door sill, often referred to as a threshold, is designed to create a barrier at the bottom of a doorway that helps direct and manage water that may enter from outside. This is particularly crucial in areas prone to rain or flooding, as the sill allows for water to flow away from the door and not seep into the interior of a building.

By incorporating a slight slope, the sill promotes proper drainage, helping to protect the structure from water damage, mold growth, and deterioration of building materials. This function is vital for maintaining a dry and comfortable indoor environment, which is why the design and materials used for door sills are selected for their water-resistant properties.