While helping the Priest manage the church, you'll find that you can upgrade the fence a few times. The first one will be replacing the old rungs on the fence with new wood, while this one is the second upgrade and you'll need a mixture of polished and carved stone to make this. You'll need 24 polished stone, 2 carved stone, and 12 complex iron parts to reach this upgrade, but it is a nice bonus to your cemetery points. It will provide +20.