Beekeepers use these queen clips to place queens in a safe place while manipulating frames, removing bees from buildings, or in other situations when they want to confine the queen.
The spring-loaded clip can be opened to allow the queen to be placed between the sides of the clip. The slots are wide enough that a worker can pass through but small enough that the queen cannot.
The metal design makes it more durable than the plastic clip, but it is slightly more expensive. The clip can safely be placed in a pocket to keep the queen safe while working.