What is the hollow in the face of a brick called
Brick although the brick may be "frogged," having indentations on one of the longer faces), "perforated" (containing a pattern of small holes through the brick, removing no more than 25% of the volume), "cellular" (containing a pattern of holes removing more than 20% of the volume, but closed on one face), or "hollow" (containing a pattern of large holes removing more than 25% of the brick's volume). Blocks may be solid, cellular or hollow The term "frog" can refer to the indentation or the implement used to make it. Modern brickmakers usually use plastic frogs but in the past they were
Hollow-Face illusion Hollow-Face illusion The Hollow-Face illusion (also known as Hollow-Mask illusion) is an optical illusion in which the perception of a concave mask of a face appears as a normal convex face. While a convex face will appear to look in a single direction, and the gaze of a flat face, such as the Lord Kitchener Wants You poster, can appear to track a moving viewer, a hollow face can appear to move its eyes faster than the viewer: looking forward when the viewer is directly ahead, but looking at an extreme angle when the viewer is only at a moderate