Card-Jitsu Belts are clothing items you get as you progress to the ninja status. There are nine different belts to earn and collect. The white belt is the lowest, while the black belt is the highest. These are some of the most common items in Club Penguin.
It is much easier to get belts since the recent updates. When a penguin gets a Black Belt, they have a chance of beating the Sensei in Card-Jitsu. When they win, they become a ninja. Many penguins give up fighting the Sensei, even though you have to fight and lose to him several times before you become a ninja. There is a trick to beating him, though.