Atama-tsunagi (頭繋ぎ) – a horizontal board or similar material, that connects several vertical columns at the top. Atama means “head” or “top”, and tsunagi means “to connect”. When used in the context of conventional Japanese construction, atama-tsunagi is generally either temporary or non-structural, while the term hari is used for the large, horizontal beams which are permanent and structural.
However, when used for 2 by 4 house construction (cap plate), atama-tsunagi is both permanent and structural, as, while the 2 by 4 lumber is layered to collectively form a larger beam, a single 2 by 4 on its own wouldn’t qualify as one and it therefore would be argued that this term is more appropriate. The images above show the 2 by 4 framing form of atama-tsunagi.