# Vertices not behaving smoothly after Subdivide

This model was made by extruding 2 Bezier curves. I tried joining them at the four vertices but the subsurface doesn't work.

This is the result. I've tried to delete and recreate the vertices several ways but I always get the same or similar result.

• This looks like the normals are flipped on half of the model, so subdivision surface claims the outermost edge as the interpolated midpoint between these faces. – Allen Simpson Feb 22 at 16:11