you have to UV map them. Even if they are a slightly different shape, if they all have the same number of vertices and edges and so on, you can use the same UV Map. The problem is that if you don't, you end up with a tangled web of death as your UV map and you'll get nothing sensible out in terms of textures when you try to apply one. For posts you might be able to use cylindrical or auto mapping and get reasonable results without doing anything else.