Hi Matt,

> I've created a circle, then projected it onto the side of
> a cylinder. Then I select the circle, click Blend, the select
> the circle that I projected earlier then hit done.

Could you please attach a .3dm file with your circle and cylinder in it that you are talking about?

It is a lot easier to see what is happening when looking at the same model, rather than just a text description...

But probably my guess is that you're running into a problem of having a "standalone" curve object that is directly on top of the surface edge, which prevents you from selecting the surface edge easily.

If you want to do a blend between surfaces, you have to select surface edges for that, not "curve" objects that are separate from the surface. Basically, before doing the blend try clicking on that curve when there is nothing selected. If it selects then, that means it is a separate curve object and not an "edge" - delete that separate curve so that you can select the edge and then you'll probably be able to do the blend.

But if you can post the model file it would make it easier to know if that is the problem or not.

That "curve on top of edge masking selection" is kind of an easy problem to run into, it tends to be a good idea to delete or hide those curves after you are done using them so that they don't get in your way.

- Michael