Push-In Cages are a tool for introducing queens to aggressive colonies. Aggressive colonies will often kill a new queen. This tool gives the bees more opportunity get to know her and space for her to lay her own eggs in the comb during the introductory period. This gives you the opportunity to monitor hive behavior upon her release.

The cage is made of 1/8″ hardware cloth which can be cut and folded to a size that fits your frame size. Usually a 3×3″ is enough. But you can vary that to your preference. The wire fabric is stiff with sharp edges, so use gloves. All you need is a strong shears or tin snips to cut it. It is bent by fingers and you can use staples to secure the edges, but it is stiff enough that staples are not really needed. I bought a roll of 6″ x 25′ in the roofing section at Home Depot for $16.00. More than I needed. But the smallest amount I could find.
The cage should be pushed into a section of brood comb with empty cells and perhaps some emerging brood. Release the queen into the cage and close it up behind her. Check for colony acceptance after a week.

This cage can be reused over and over. You can make larger cages as well. Just make sure that there is enough room for the queen and all the brood that will be emerging during that time. Try to have only a few capped cells and more empty cells if you can.