An expression I don't understand
This is an excerpt of a book Shawshank Redemption
In early1959 a new warden was appointed, and a new assistant warden, and a new chief of guards. For the next eight months or so, Andy was just another con again. It was during that period that Normaden, the big half-breed Passamaquoddy, shared Andy's cell with him. Then everything just started up again. Normaden was moved out, and Andy was living in solitary splendor again. The names at the top change, but the rackets never do.
What does "the names at the top change, but the rackets never do" mean?