Hi Brendan,

> The seam occurred after I carried out the Loft command. Perhaps I forgot to carry out
> a Join on that rail?

Every closed surface has a "seam edge" in it which is a normal part of the surface's structure and can't be deleted. Basically every NURBS surface has an inherent rectangular structure to it like a rubbery sheet of paper. With a closed surface it's like if you took a sheet of paper and rolled it into a tube with 2 opposite sides touching each other. There will be a "seam edge" in that closing spot.

I had thought you were referring to all the small edges running across this area here:




That area of your model looked to me like it came from a boolean cut from a side profile curve, and probably the side profile curve is made up of numerous segments in it. If you wanted to get rid of some of those edges you could run the Rebuild command on your cutting curve before doing the boolean with it.


> Am I correct in thinking that a Join will make all the curve segments into one curve?

It does make it into one curve but the curve is sort of like a group that retains the original segmentation. If you use Edit > Separate on the curve you can see that it breaks apart back into the original segments.

If you want to remove segmentation and fuse adjacent smooth segments into single segments, the Rebuild command can be used to do that.

- Michael