Especially an elongated boss (carved keystone) at the junction of the intersecting ribs of the fan vaulting associated with the English Perpendicular style.
尤其是指与英国垂直式风格有关的一种扇形拱顶的交叉拱肋在接合点的拉长浮凸饰（雕刻的楔石）。
2
Can be incorporated in junction boxes or retrofitted in 503 style boxes.