Extruded edge problem I am an absolute beginner with Blender. I have a question about extruding meshes.
I have done a simple extrusion on a subdivided plane. However opposing corners of the model have different shaped corners. I want understand the logic behind this result.

I am using Blender 2.79

I created a plane mesh.

Subdivided the plane a few times.

Highlighted the faces I wanted to extrude.

Extruded to create a pyramid (or dish when inverted).

Result - two diagonally opposite corners have sharp edges.
The opposing diagonal corners have chamfered edges.
I don’t necessarily prefer either edge type. I just want to understand why Blender has produced two different results on what I feel is a uniform mesh.
You didn't extrude, you probably pressed g and moved it along the z axis.

Your mesh should look like this: