Weak colonies with two or three frames of bees should not be reversed at this time. When the colonies are weak like this, the bottom box should be removed and the hive should just be in one deep at the moment. This will make the hive easier to keep warm compared to a two deep hive. If a beekeeper has another strong colony, it would be helpful to take a frame of brood sometime later in April and add it to the weak colony. This little increase in brood can turn around a weak colony and it will start increasing the bee population almost immediately. The extra bees will aide in covering more brood, this will give the queen a better opportunity to increase egg laying.
New Package bees are reversed usually only once in June.
The first reversal on a three deep colony should go like this. The three deeps are numbered to keep it straight in this example.
Boxes:
1 should end up with 3
2 1
3 2
After this first reversal on a three deep hive setup, any new reversals will be switch the bottom box with the top box.