It can be crafted in your Crafting Menu (default key "Q") or at any Crafting Table in worlds created before R22 on September 16th 2015, after the recipe has been unlocked upon buying it. The blocks will appear in the crafting menu in the "build" section under the headline "medieval".
The Medieval Spike Wall was introduced on May 1, 2017 during the R41 update. It is unique (so far) among wall and floor blocks as it has a 3D effect with the spikes sticking out of the block outlines (like wildwood flowers stick out of the flower block).
The block consists of a light grey stone block banded with slightly weathered dark bluish-grey metal bands and a large pyramidical spike on each side. The metal bands also have a 3D effect, although less noticeable than the spike. The spikes do not deal damage and don't impede movement over the block.
To craft a stack of 8 Medieval Spike Wall blocks, you will need
- 2 stone
- 4 iron rods (crafted in the processor)
- 1 iron slab (crafted in the processor)
- 2 melted wax (either created in the forge or found in chests)
The block can be rotated by pressing and holding R and moving the mouse while holding the left mouse button.