Reply To: What am I doing wrong?

HI joebods, this is called an N-gon (not because of its shape, but because it has more than 4 Edges):

N-gons can give problems when subdivided, especially when they are concave.

One way to fix this is to make everything into triangles before subdividing and Blender can do this for us.

Now, I like to work with Modifiers, so I beveled through a Modifier, so I could correct/change which Edges get Beveled, but you can also use CTRL+B if you want.

I ‘marked the Edges I wanted to Bevel with CTRL+E > Edge Bevel Weight, set to 1 (the blue Edges here):

Then use a Modifier stack as seen above: first Triangulate (Quad and Ngon Method set to Beauty), then Bevel (Limit Method set to Weight) and finally a Sudivision.

When happy with the result, Apply the Modifiers (top to bottom) and do the dirty vertex colors: