What a kugikakushi is
A kugikakushi is a decorative metal cover placed over the head of a nail fixing the Nageshi or similar trim. It conceals a fastening that structure requires, and it is treated as ornament in its own right.
Some carry a family crest. The Tomita Residence in Ibaraki Prefecture, from the early Meiji period, is described as Irimoya-zukuri with Sangawara-buki and boldly projecting eaves, with a large Doma and living room to the north and three Zashiki to the south beyond an entrance room, the innermost projecting as a wing; its nail covers bearing the crest of the Kasama domain lord, together with its Osa-ranma, mark the interior as formal Shoin-zukuri.
What is worth noting is that the entry cites the nail covers alongside the transoms as grounds for calling the room formal. The design of a small metal fitting is treated as evidence of the standing of the room.
Using a domain lord's crest says something about the household. That a farmhouse displayed one indicates the family's relationship with the domain.
Where to look
Follow the line of the trim above the openings. Metal fittings at even intervals where it crosses the posts are the covers, and since the trim runs round the room they are easy to find once you look up.
Besides crests, floral and geometric designs are common. The metal is usually copper or brass, often gilded.
Houses in Sukiya-zukuri omit the trim itself, and with it these fittings. Trim and covers together place a room in the formal tradition.
Records mention them rarely. The structure field states the roof and the size; fittings appear only in the descriptive text, so municipal survey reports are worth consulting when researching them.
References
- Agency for Cultural Affairs: Registered tangible cultural properties (structures)
- https://www.bunka.go.jp/seisaku/bunkazai/shokai/yukei_kenzobutsu/toroku_yukei.html
- National Cultural Properties Database: Tomita Residence, nail covers bearing the domain lord's crest in a formal reception room
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00014319
Last verified: 2026.09.03