Brushes are essential tools in tying flies for fly fishing, used primarily for applying and shaping various materials such as feathers, fur, and synthetic fibers. These brushes help blend and secure materials, creating lifelike patterns and textures that mimic natural prey. They can also be used to add fine details and ensure even distribution of dubbing or other tying materials. By manipulating the materials with brushes, fly tiers can craft realistic, durable flies that effectively attract fish.