The cabinet, vertical spacer and the top are all built separately. The vertical pieces have cap on the top similar to an upercase T. The upper part of the T has a dado for the vertical section to fit into. The upper part is screwed into the bottom of the top. I did it this was so the top doesn't have any holes to try and fill. The cabinet section is screwed into the bottom of the vertical pieces.
Here is picture from the underside
Let me know if you have any other questions.
Here is picture from the underside
Let me know if you have any other questions.