4 Way Contuinity Tiles
Four-way tiling is a texturing trick that allows a texture to be rotated 90° and/or flipped on adjacent polygons, but still tile with itself. The texture is edited so that each of the four edges will tile with each other.
The benefits of this are to hide the tiling artefacts from features that repeat across the surface and it allows the artist to use less texture memory because they don't have to use multiple textures for the same effect. The downsides are that this creates a little bit of the Rorshach/butterfly effect on the texture borders, and it also increases the vertex cost of the model since each rotated UV will duplicate the texture vertices along its seams.