Source: In common use
Shihōzume-gitae (四方詰め鍛え) literally means "four sides packed forging".
Similar to the hon-sanmai construction but with the addition of a separate section of so-called munegane (棟鉄 / 棟金) at the back.
See the tsurikomi article by the Kashima sisters. Also Markus Sesko; Encyclopedia of Japanese swords. Lulu Publishing. 2014. Page 390. (Available for purchase here.)
Article: Construction methods of Japanese swords