Searching about some tilesets for a little RPG game, I've often found these kind of tileset :
Their structure are special, there is two upper tile and 4 others for the same material. I understand that, like that, you have all what you need to create more various shapes than simple rectangles of different sizes. But I don't get how they are used in practice. I'm talking about the two little upper tiles that are used to make some corners. for me the 4 corners are stored inside only one tile ? (hard to explain with my bad english but I'm sure you understand what I mean)
Also, do you know if that tilemapping technic has a name ? And do you kown if it is possible to use them directly in Tiled ?