While you don’t need a leader, it’s cheap insurance. Taking a couple minutes to add some inexpensive, thick, and tough monofilament to the business end of your bait setup (no matter what kind of running line you use) is an easy way to help ensure you land the fish of your dreams. Catfish are tough, strong, and live in places that have lots of structure—a leader is armor that helps you overcome all these obstacles, and helps get your trophy cat to the boat or the bank.