OK as promised, here are some photos of half lap dovetail joints and their variations. The idea here is to show different approaches to the refined entry concept, which is an attempt to solve the problem of shrinkage opening up the dovetail and weakening the joint.
The concept is that, in general, a sharper angle will gap less, that is the closer the angle is to perpendicular to the grain, the less it will open as a result of shrinkage. But the flaw here is that the sharper the angle, the weaker the connection can be. The the solution is a double angle, or refined entry. Hope that makes sense. Here's pictures:
