The four sides of the mold formed the extrados, the intrados, and the two ends of the block; the other two sides being left open.
intrados: The under or concave face of the solid structure of an arch.
It was determined to attempt to stop these leaks by the application of a water-proof cement coating on the intrados of the arch.
The under or concave side of the voussoirs is called the intrados, and the upper or convex side the extrados of the arch.
The lower surface or soffit of the arch is the intrados, E, and the upper surface the extrados, F.
The inner surface, or intrados, and the remainder of the extrados are smoothly dressed (fig. 38).
In S. Sophia the vault springs from the intrados of the transverse arches, that is, from the lower edge.