Vertical intervallar structures: Longitudinal and often radial structures inside the intervallum (septa, taeniae...).
Intervallum: Space enclosed between the walls.
Aporous: No pore.
Finely porous: Pore diameter smaller than lintels width.
Lintel: Skeletal structure separating and bounding adjacent pores.
Coarsely porous: Pore diameter greater than lintels width.
Lintel: Skeletal structure separating and bounding adjacent pores.