A security grating is an obstacle present in Concourse Ventilation, a room on Eastern SkyTown, Elysia. These are a pair of retractable grates in the shaded portion of the room, in between the Wall Jump Surfaces. When active, Samus can stand on them, but they need to be removed so that she can proceed further into Eastern SkyTown. To do this, she must use a Bomb Slot mounted in the wall above each grating. The grating will then come apart in multiple sections: first, a pair of dark rings will retract, followed by three brown rings (the center one moves in an opposite direction from the other two), and finally the five support beams pull into the wall.
They remain retracted for the rest of Metroid Prime 3: Corruption.
"Security grating is locked. Use nearby control interface to gain access to lower levels."