capstone

UK
/ˈkæp.stəʊn/
US
/ˈkæp.stoʊn/

Library

How did they build the Great Pyramid of Giza? - Soraya Field Fiorio
Finally, a capstone was placed on top.
architecture
pierre de couronnement
pierre sommitale
Une pierre de couronnement est la pierre de finition au sommet de la pyramide.