凸榫

But their surfaces bear witness to homely labor: Topping the tallest stone, once part of a trilithon, is a tenon—half of a mortise-and-tenon joint borrowed from woodworking.

但巨石的表面见凡的劳：曾是三石塔组成部分最高的那块巨石有一个凸榫——是从木材工借鉴而来的半个榫臼接头。