Examples described herein include an electromagnetic interference shield. In some examples, the electromagnetic interference shield includes a wall comprised of a conductive material. The wall may have a first surface, a second surface, and a thickness between the first surface and the second surface. The shield may include a rounded opening in the wall that creates an air passageway through the thickness of the wall. The shield may also include a first obstruction in the opening and a second obstruction in the opening. The first obstruction may span across the opening. The second obstruction may span across the opening and intersect the first obstruction. The first obstruction and the second obstruction may be waveguide structures.