Hi Lanren, can you please post the 3DM model file that you showed a screenshot of and that will help me to show you what to do with it.

It actually helps a lot if you can post your model file along with your question instead of only screenshots, it's a lot easier to see what you're trying to do with a model file that can be examined from multiple angles and zoomed in and things like that.

But basically you'll use the Edit > Trim command with the "Isocurve" option to cut the surfaces to the left and right of the current hole area so that you have a wide open strip, then you would select the edges of both sides of the hole and run the Construct > Blend command to build a blend surface. You'll want to be using the current v3 beta to do this, since it has an updated Blend command that can now use more than one edge curve on either side of the blend.

- Michael