The purpose of a garden stool is to provide you with a place to sit while gardening. They are mostly made of wood, metal, or plastic, with drainage holes drilled into the seat. Water drains out of the stool through the holes, keeping the stool from getting soggy or rotting. The most common reason for having holes in a garden stool is to prevent mold from growing. Your stool's drain hole allows you to use it even when it's raining outside without worrying about getting wet!