strap bolt
A bolt with a flat, elongated head resembling a battledore (羽子板), used in construction or machinery to secure straps or plates.
This metal fitting is secured with a strap bolt.
Compound of 羽子板 (hagoita, 'battledore') and ボルト (boruto, 'bolt'), from the resemblance of the bolt's head to the shape of a hagoita paddle.