Steps for crenellation (left to right)
- Starting point
- Use the Inset Faces tool (I)
- Select outer ring of polys and extrude up the Z axis (E + Z)
- With outer ring of polys selected, choose Edge > Subdivide (Number of Cuts: 2)
- Dissolve the two interior edge rings
- Set Transform Orientations to Normal and Pivot Point to Individual Origins. Select the center polys within the outer ring and scale them down on the Y axis (S + Y).
- Select the corner polys within the outer ring and extrude up the Z axis (E + Z)