“Should the king abscond, the keystone of the whole constitution would be lost, with incalculable consequences.”

“The arch features a decorative keystone and double corbels, outlined by antique glazing on a white lacquer base.”

“We must be careful, however, not to paint a picture of historical evidence that suggests that newspapers are the keystones of such documentation.”

“It is only after close study that apparent solecisms can be interpreted as the keystones of a highly conscious literary construct.”

“Each wall contains a walk-through arch marked by massive keystones that were hand worked onsite.”