There are lots of plans for swarm capturing gadgets-boxes or buckets on poles, sacks, and bee vacs. They all have their advantages, but the simplest device that will cover 95% of all swarms is a cardboard box.
Cut a window in the side and duct tape some window screen or 8 mesh hardware cloth over it to prevent suffocation. Make several boxes. If you catch most of the bees in the first box but miss the queen, you’ll have a smaller cluster to catch on the second try. You may also get more than one swarm a day and it can be frustrating to run out. It’s a good idea to weigh the boxes when empty and mark the weight on the box. Then you can weigh the bees and know how big a swarm you’ve caught.
When working with swarm boxes, remember that if the queen is in the box, most of the bees will enter the box voluntarily, so you can leave it cracked open. If the general movement is out of the box, use duct tape to close it. Catch the rest of the swarm in a second box. The box containing the queen will usually have extra bees gathering on the screen so you can usually guess which one she is in.
Turn the boxes upside down so the bees will cluster on the box’s floor. It’s easier to shake them into a hive if they aren’t sticking to the box flaps.
A swarm is like package bees. There won’t be any new bees for three weeks. In the meantime the colony dwindles quickly. A large percentage of swarms won’t survive without help. Give them a head start by feeding them 1:1 (1 qt. sugar to 1 qt. water) sugar syrup.