Which tool is commonly used to create curls in the hair?

The tool commonly used to create curls in the hair is the curling iron. This device typically features a heated barrel that allows you to wrap sections of hair around it, which in turn creates defined curls or waves. Curling irons come in various sizes, so they can produce different types of curls, from tight ringlets to loose beachy waves, depending on the diameter of the barrel and the technique used.

Flat irons are primarily designed for straightening hair; while they can be used to create curls with a specific technique, they are not specialized for that purpose. A blow dryer is mainly used for drying hair, and while it can also assist in styling, it does not inherently create curls without the use of additional tools like a diffuser or specific styling brushes. A round brush is typically employed during blow drying to add volume and shape to hair but isn't a tool designed to create curls directly. Therefore, the curling iron stands out as the most effective and specialized tool for creating curls.