Upright: Usually 6" or 8" thick and placed on a base stone which is then placed on a concrete foundation. They come in many shapes, both standard and custom, such as boulders, jagged slabs of granite, pyramid-shaped, etc.
Slant Memorials: These are thicker at the bottom and taper to the top. The face of the stone is at about a 60-degree angle. They can be used with or without a granite sub base.