See also: Creating Surface Fillets
A surface fillet creates a smooth blend between intersecting surfaces - a primary surface, and one or more secondary surfaces. The Fillet command creates one curve on each surface the fillet touches, following the curve of the intersection.
When a fillet surface is created, a surface curve is generated on each of the intersecting surfaces to mark the boundary of the fillet. This then allows you to use a Trim Surface (Edit menu) command to trim each surface to the edge of the fillet.
A fillet surface can be intersected, trimmed and filleted in the same way as any other surface type.
The properties of a Surface Fillet can be altered using the Entity Data (Edit menu) command.