from bush farms website:
"Opening the broodnest
This, of course is what we want to do. What we need to do is interrupt the chain of events. The easiest way is to keep the brood nest open. If you keep the brood nest from backfilling and if you occupy all those unemployed nurse bees then you can change their mind. If you catch it before they start queen cells, you can put some empty frames in the brood nest. Yes, empty. No foundation. Nothing. Just an empty frame. Just one here and there with two frames of brood between. In other words, you can do something like: BBEBBEBBEB where B is brood comb and E is an empty frame. How many you insert depends on how strong the cluster is. They have to fill all those gaps with bees. The gaps fill with the unemployed nurse bees who begin festooning and building comb. The queen will find the new comb and about the time they get about ¼" deep, the queen will lay in them. You have now "opened up the brood nest". In one step you have occupied the bees that were preparing to swarm with wax production followed by nursing, you've expanded the brood nest, and you've given the queen a place to lay. If you don't have room to put the empty combs in, then add another brood box. The other upside is I get good natural sized brood comb.
A hive that doesn't swarm will produce a LOT more honey than a hive that swarms.
Checkerboarding aka Nectar Management
Checkerboarding is a technique from Walt Wright that involves interspersing drawn and capped honey OVER the brood nest. It in no way involves the the brood nest itself. If you'd like to know about this technique and a LOT more detail about swarm preparation and what goes on in a hive at any given time in the buildup, I would contact Walt Wright. This is a method that also fools the bees into believing that the time has not yet come to swarm. It works without disturbing the brood nest. Basically it's putting alternating frames of empty drawn comb and capped honey directly ABOVE the brood nest. If you would like to purchase a copy of Walt's manuscript, it's about 60 pages long and last I heard was $8 in a pdf by email or $10 on paper. You can contact him at this address: Walt Wright; Box 10; Elkton, TN 38455-0010; or WaltWright_at hotmail dot com (Encoded to avoid the spambots. Don't forget the underscore).
Also there is more on checkerboarding here: Experiment"