Expanded metal is a material with openings in its surface that are created by a simultaneous interplay of offset cuts with expanding distortion of shapes. The result is a grid that is neither welded nor braided, that has internal structural integrity and that is independent of the size to which the expanded metal is cut.
When planning an expanded metal ceiling, ensure that any normally expanded version has the three-dimensional properties that enable the ceiling pattern to appear open or closed, depending on direction of view. This case involves a tunnel direction.