Grating section

The grating section, or upper grating section was the part of a Dalek's casing below the dome and above the weapons platform. (PROSE: The Dalek Generation) Kaled mutants were typically located within the grating section, beneath the dome. (TV: Dalek, Daleks in Manhattan)

Should a Dalek chose to open their casing, the front portion of the grating section would extend and split in two, exposing the mutant inside. (TV: Dalek)

Variants
Matching the casing, the frame of the "bronze" Dalek drones of the Last Great Time War, as well as the Emperor's Personal Guard, and beyond were coloured bronze. (TV: Dalek, The Parting of the Ways) While Black Daleks such as Dalek Sec had matching black frames, (TV: Army of Ghosts) black Dalek Inquisitor Generals such as Dalek X likewise had black grating sections, though they were distinguished by their gold slats and sensor globes. (PROSE: Prisoner of the Daleks) Red Supreme Daleks had golden frames which uniquely connected the grating section to the weapons platform. (TV: The Stolen Earth)

Matching the casing, the frame of the Ironside Daleks' grating sections were coloured khaki-green. (TV: Victory of the Daleks)

The Daleks of the New Dalek Paradigm, Supreme, Eternal, Strategist, Scientist and Drone, were distinct in that their taller grating sections which had no frames, consisting of four black collars. (TV: Victory of the Daleks) The grating section of the Daleks following total event collapse, along with the rest of their casing, was weathered to stone. (TV: The Big Bang)

Behind the scenes

 * Curiously, those bronze Daleks dubbed as "Aristotle Daleks" in the Doctor Who: Legacy mobile game are distinguished by white grating sections which do not appear in Into the Dalek.