When managing your hives using traditional Warré methods (by nadiring, or adding boxes only to the bottom of the hive), you don't typically need to use a queen excluder for any reason. However, there are a few scenarios where you might want to use this device. It's primarily used as a queen locator when re-queening your hive, but it can also be used as a queen excluder when supering. If your hive consists of at least three boxes of drawn comb, you usually don't need to use an excluder if you super it. But if your hive is small (only two hive bodies), you may want to use an excluder under any box that you add to the top, in order to keep the queen from laying eggs in it. Lastly, if you're wanting to expedite honey harvesting and there is still some brood in the box(es) that you'd like to harvest, you can place an excluder under that box so that the queen cannot get up there to lay eggs in it anymore.