Japanese castle walls, Sangizumi

The external walls of the Japanese castles were made of stones fitted together without mortar, and the wall's aspect varied greatly depending on the technique used, from the coarse nozurazumi to the finer uchikomihagi, and to the very smooth (and expensive) kirikomihagi.

Another such technique, called sangizumi, was used to increase the stability of the exterior wall corners: rectangular stones, carefully shaped, were assembled in a zipper-like manner, as you can see in this photo, taken at the external wall of the Hiroshima Castle.