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
Typically, the frames of the grating sections of most Daleks were coloured to match their domes. (TV: The Daleks et al.) Notable exceptions were the black-domed Dalek saucer commanders and the Emperor's Personal Guard, which were coloured according to their wider casings, (TV: The Dalek Invasion of Earth, The Evil of the Daleks, The Parting of the Ways) and the early Supreme Daleks, whose frames were coloured silver like the silver Daleks they commanded. (TV: The Dalek Invasion of Earth)

The white Imperial Daleks created by Davros uniquely had golden grating sections with white frames. (TV: Revelation of the Daleks, Remembrance of the Daleks)

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)

The Dalek Time Controller was distinguished by its taller upper grating sections, which were diagonally circled by revolving rings. Like the whirling debris fields around a gas giant, they appeared solid from a distance, but a closer look saw them burn with the energy of the Time Vortex unfolded in the open gateway within the section of the casing. (PROSE: The Dalek Generation)

As a target
Though the common weakpoint of the Dalek casing was understood to be the eyepiece, (TV: Resurrection of the Daleks, Remembrance of the Daleks, Dalek) numerous Daleks were destroyed upon sustaining hits, typically from energy weapons including Dalek gunsticks, directed at their grating sections.

In the Death Zone on Gallifrey, a Dalek inadvertently destroyed itself while attempting to kill the First Doctor within a hall of mirrors, with a beam ricocheting and striking its grating section, blowing apart the top half of its casing. (TV: The Five Doctors)

During the first confrontation between the Daleks loyal to Davros and those loyal to the Supreme Dalek, they destroyed each other by hitting their grating sections, resulting in their casings being blown apart. (TV: Resurrection of the Daleks)

On Necros, Natasha Stengos killed her father Arthur Stengos, at his request, by firing a laser beam at the grating section of the glass casing which housed his mutated form, blowing it apart. Elsewhere, the DJ used an ultrasonic beam to destroy two of Davros' Daleks by striking their grating sections, breaking them apart and blowing off their domes. (TV: Revelation of the Daleks)

At the Papal Mainframe during the Siege of Trenzalore, rogue Dalek puppet Tasha Lem used the gunstick embedded into her hand to kill three Daleks in quick succession by striking their grating sections, causing their casings to be engulfed in flames. (TV: The Time of the Doctor)

Aboard the Aristotle, Rusty, the "Good Dalek", killed several Daleks by striking their grating sections. (TV: Into the Dalek)

Behind the scenes

 * In the theatrical film Dr. Who and the Daleks (held to be an invalid source by this Wiki), the Black Dalek and the Red Dalek had grating sections with gold frames. Their subordinate Blue Daleks had grating sections with silver frames.
 * In Daleks' Invasion Earth 2150 A.D., all Daleks have grating sections with silver frames.
 * 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.
 * In Dalek Hack, the player has the option to change the colour of a Dalek's casing which is divided into three sections, including the dome attached to the grating section.