1. First, pour some laundry detergent into a container, pour in an appropriate amount of warm water and stir to let the water and laundry detergent merge.

2. Disassemble the cap, apply laundry detergent to the stained area, and soak the cap in the solution.

3. After about 10 minutes, use a brush to clean the inside and outside of the peaked cap.

4. Rinse the clean cap in clean water.

5. The peaked cap, also known as the duckbill cap, is characterized by a flat top and a visor. The brim of the hat ranges from two inches to four inches, and the width also varies. The peaked cap was originally a hat worn by hunters when hunting. Therefore, it is also called a hunting cap. Because of its flat brim like a duck's bill, it is also called a peaked cap.