DESCRIPTION: This close up of the right side shows the thickness of the exit hole wall. It is 8 inches of brick with steel mesh and rebar. There is some question regarding what was behind the mesh due to the fact that this was in the unrenovated portion of the Pentagon. Because of the alleged angle of travel, the impact zone was in the renovated portion on the outer wall of "E" ring and the exit hole was in the unrenovated section of the "C" ring wall.

DESCRIPTION: This close-up of the left side shows another view of the exit hole wall. If something solid came through, then how did it break the brick without clearing the pipe, steel and the mesh?

"The construction of the 'exit hole' wall is fairly straightforward. The structural portion of the wall is obviously brick. Inside of the brick wall is what is referred to as a furring wall (or firring wall; both are used and I'm not sure which is correct), in this case using an old system of lath and plaster (today steel studs and drywall are typically used). The upright and horizontal black iron members are wired together, and the mesh is then wired to that grid-like system of framing members. Plaster is then applied over the steel mesh. The furring wall serves two purposes: it provides a finished interior surface that can be painted, wallpapered, etc., and it provides a means of bringing concealed electrical and plumbing down the walls, since there is typically an air space between the exterior wall and the furring wall. The reason that it appears as though there is plaster between the framing members and the mesh is because the first coat of plaster oozes through the mesh, thus locking it on. The actual sequence, from exterior to interior, would be: brick wall, airspace containing plumbing and electrical systems, metal cross members, steel mesh, and then plaster. The preceding description is from Dave McGowan - General Contractor, who also has a great site with 9/11 information. Center for an Informed America