Henry (Raleigh NC)
Unsure of your exact question...
The tails are cut the same way as through dovetails, but not to full thickness of the drawer side. One end of these tails is in fact 'rounded', the portion that is inserted into the socket; it's a convex curve (when cut with a router/jig.
Then the sockets are cut into the drawer front with a height and depth to match the height and depth of the tails. These sockets have a rounded 'interior' end as well - a concave curve (when cut with a router).
These matching curves are buried (internal to the joint) and not seen.
Hope that helps - I am sure a diagram would help but a browser search ought to give you that,