Thanks Michael. I was originally trying to fillet that side, but it wouldn't take, so instead I *grabbed* the edge of the armrest, extended the front and back with tangent lines and then swept a perfect aligned 'cutter' -- or so I thought. Why wouldn't the cutter be aligned correctly, especially since it was generated from the originating curves and started from the Z direction?

I kinda hoped, as a last resort, the sweep along a path and boolean subtract would work instead of fillets. Guess I should rethink. Thanks for the tip on Construct > Curve > isect !! :-)

Hi Chipp,

> Why wouldn't the cutter be aligned correctly, especially since it was generated from
> the originating curves and started from the Z direction?

If you turn on the surface control points for both pieces, you should see that they are not 100% identical - sweeps are constructed by an adaptive fitting process that refines the generated surface repeatedly until it is within an acceptable tolerance. The result that you get from a sweep won't be the 100% exact same result as one from an extrusion for example. So in a case like you've got there, you end up with 2 very similar yet still not identical surfaces that overlap right on top of each other. Such things are generally difficult for booleans to deal with.

There are other methods that produce exact geometry from curves, like for example Extrude. But Sweep goes through a fairly different process.

- Michael