Is the cavity in frogged bricks present to reduce the amount of clay needed to make them? But it is then substituted with mortar so isn't that the same?
Or is it present to increase the surface area the adhesive mortar will join to (and a wedge) and thus achieve a better joint and more resistant to lateral forces?
Or is it present to increase the surface area the adhesive mortar will join to (and a wedge) and thus achieve a better joint and more resistant to lateral forces?