It's possible you're thinking of one of these:
* The "Pokeball" trick for getting rare Pokemon: This refers to the strategy of using the correct Pokeball for the situation. For example, a Great Ball is more likely to catch a Pokemon than a regular Pokeball, and an Ultra Ball is even better than a Great Ball.
* A specific "Pokeball trick" found in a Pokemon game: It's possible this is a specific glitch or strategy in a particular Pokemon game that's not widely known. It would help to know which Pokemon game you are asking about.
* A trick used in a Pokemon-themed game or application: There are many Pokemon-themed games and apps available, and some may have their own unique "Pokeball trick".
To help me understand what you are asking about, please give me more information:
* What game are you referring to? Is it a specific Pokemon game, or another game/app?
* What is the goal of this "Pokeball trick"? Is it about catching Pokemon, or something else?
With more context, I can hopefully give you a more specific answer.