Gaps and Holes in Sculpties (using Maya)

I recently took the basic Maya 101 class at Xeniversity and now am using Maya pretty much exclusively for creation of sculpted prims for Second Life. He mentioned a few times about hiding parts of the sculpty in such a way that it wouldn't be rendered, allowing you to create "gaps" in your sculpties.
I've been trying (in vain so far) to accomplish this, but am having no luck. I don't know what I'm doing wrong. Now that the classes are over, I don't want to have to bother him with constant questions about this and that in Maya, as I've already had to do it since the classes ended, so I'm hoping for help here in the forums.
I am attaching a screen shot of what is happening when I upload my "gapped sculpties." Basically when I upload them, and even when in Maya, I see a little triangle of prim left over at the bottom/top of the two peices I created with the gap.



And here are photo examples from inside Maya of a second trial with getting a gap:

To create a sharp corner with NURBS, it takes three overlapping rows of vertices (hulls). Remember, NURBS are curve-based. So unless you overlap vertices, you'll always get a smooth interpolation between points, rather than an angular one.

Park three hulls on the end points of the line between the two parts, and that triangle should go away.

If you sign up for Xenius's advanced class, by the way, I believe he covers topics like this.

I plan to once he opens up registration and thanks for the reply!

I had only used 2 hulls at each end of the line so I will do 3 and I'm sure that will solve my problem.