Hi Mike, thanks for the file - but without being able to also go through the steps of constructing the surfaces, the only information I can really give you is that "yup, you're right they don't meet" - the reason why they don't meet has something to do with the specific method used to construct them. It could be a bug there, or like I mentioned if you use Network in v2 it can tend to make things that don't meet in this type of way but that has been tuned up in v3 already.

According to the curve deviation tool in Rhino those edge are 0.007 units apart, so yup they're just very slightly outside of the join threshold.

If you do the scaling trick as mentioned above to scale both surfaces down by 1/10 in size, then they will join though because then the gap between them is only 0.0007 units and below the join threshold. To do the scale select them both, then run Transform > Scale, at the first prompt for the scale origin type 0 and push enter to specify 0,0,0 as the scale origin point, then at the second prompt type in 0.1 for the scale factor and push enter - now with your objects scaled down they will join and you can scale back up in the same way with a scale factor of 10.0 this time to restore to original size.

I would need to have reproducable steps for the actual construction of the surfaces in order to give you any more detailed information about _why_ they don't join up, right now looking only at the final result it's pretty hard for me to know what went on previously in the construction to end up with that.

- Michael