Your table leg may not use the 1/2 width as shown. The vertical may be deeper than half. The width of the cut is simply the width of the stock. The depth of the cut is whatever you choose to make it 1/2, more or less.
Bret has made for some really cool joinery. Look in Bret's My Photos.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)