Hey, thank you for your reply. I did that, to no avail. However, when I joined and then did a merge instead, I got the results I was looking for. Weird.

I will definitely post my file next time, and thank you again.

Hi Lee, yes that helps a lot if you can post your .3dm model file instead of only a screenshot. That then allows a close examination of your geometry and also tests on it neither of which can be done on just a screenshot.

It sounds like you've got this all set up ok but the main way to handle a case like that is to make sure the main object you are working on is a closed solid.

When you do a boolean on a closed solid then the "side walls" of the cutting object will be automatically left behind and you then don't have to do any additional work to close up such things.

When your base object is not a solid then a boolean difference will only cut up surfaces and not be able to form a solid result automatically, like you are describing.

The booleans are mainly focused on working with solids, they use which solid volume a piece is in to determine which areas to keep and discard. If your base object is not a closed solid then there are no volumes to work with and the boolean will only work as a surface operation instead.

- Michael

Hi Michael,

Sorry, I just saw this, as I appear to have failed to subscribe to my own post.

I have attached the component that I was unable to close properly. I have since rebuilt the part, but it would definitely be nice to know what I was doing wrong.

Thank you for your help.

Just make sure you selected ALL parts of your curve (some are small in the fillets) and use blend to do the close, works like a charm...

Hi Lee, thanks for posting the file. So in your model one side of the hole area does not appear to be entirely planar. So I think that's why an extrusion from one side to the other is not joining in well.

If you use something like a Loft between the 2 sides that should join in ok in this case.

It's also possible to fill in holes like this by removing trimming boundaries, there is some information on doing an "untrim" here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=444.4

And there is a tutorial on this kind of process here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=446.17

- Michael

Thanks Death. Right on. The test now would be if you could boolean subtract from it now. No matter how I close it, when I try the boolean difference the result is an open mesh.

Thank you Michael - Makes sense. I'm still getting the hang of this, so my models are a bit sloppy.

I will visit the two links you provided. I appreciate the help.

Ok, I think your problem is that you do NOT have a solid when you do the subtract.
I used the surface and then blended the bottom edges (2 opposite edges, 0 Bulge),

then I did the same with the front and back openings.

Now Union the the thing and you get a solid from the which you can Boolean whatever you want...