Base unit

The base unit or travel unit was the lower section of a Dalek casing, located immediately below the weapons platform, which was studded by sense globes. (PROSE: Prisoner of the Daleks, Revelation of the Daleks, AUDIO: The Dalek Conquests) It served as a Daleks' means of mobility, via the motive unit, and ascension to hover position, via the elevation unit's antigravity mechanism (PROSE: Prisoner of the Daleks) with Dalek thrusters. (PROSE: Engines of War)

Davros' chair typically appeared as a black base unit with silver sense globes. (TV: Genesis of the Daleks et al.)

While speaking with Davros, the Twelfth Doctor openly mocked the base unit, claiming that for a "genius scientist", Davros could not invent legs. (TV: The Witch's Familiar)

Characteristics
Should a Dalek chose to open their casing, the front portion of the base unit could split its panels apart. Though this was not always executed, (TV: Dalek) it proved necessary for Dalek Sec to do so during the Final Experiment, as it allowed his new Human-Dalek form to walk out of the casing. (TV: Daleks in Manhattan) Likewise, a Dalek's casing was completely opened to accomodate Clara Oswald. (TV: The Witch's Familiar)

The Earthmen Detector was equipped onto the casing through a band encircling the base unit. (COMIC: The Daleks Are Foiled)

Sense globes
Sense globes were evidently the instruments of the Dalek self-destruct process; the Dalek named Metaltron ejected all its sense globes to create a field in which it was completely destroyed. (TV: Dalek)

One Dalek, a recon scout, built itself a new casing in 2019 Yorkshire which had short-range missiles behind each globe. One of these missiles made short work of a tank which sought to destroy the Dalek. (TV: Resolution)

During the 41st century conflict against humanity, a Chief Strategist of the New Dalek Paradigm was connected to its command ship via numerous wires and cables which were fitted to the sense globes of its base unit. They interfaced the Chief Strategist into the computers, and even allowed it to see the battle from the point of view of the drones fighting. (COMIC: The Only Good Dalek)

Similarily, a Black Dalek was connected to Survey Ship Sigma. (COMIC: The Dalek Project)

Variants
The immense Emperor who resided in the Dalek City had a distinct, tall base unit beneath the dome. This base unit was connected to the city via several tubes, and sported a unique arrangement of sense globes. (TV: The Evil of the Daleks)

As Emperor of the Imperial Daleks, Davros' casing had a base unit identical to his subordinate Daleks, underneath the larger, spherical dome which encased him. (TV: Remembrance of the Daleks)

The dome of the bronze Dalek Emperor of the Last Great Time War was supported by a frame resembling a massive base unit, complete with sense globes. (TV: The Parting of the Ways) The blue Emperor of the New Dalek Paradigm who resided on Kaalann had a near-identical frame. (GAME: City of the Daleks) A later Emperor had a similar casing which was encircled by rings of sense globe panels. (GAME: The Eternity Clock)

The dark green, robotic Proto-Daleks, which were constructed by the British and Germans as part of the Dalek Project during the First World War, had different base units; the British Proto-Daleks had only three sense globes on each panel of their base unit — with two bulky midsection rings replacing the upper set of spheres, while the German Proto-Daleks' bottom half was adorned with several flat, hexagonal plates in place of the usual sense globes. (COMIC: The Dalek Project)

As a distinguishing feature
As well as a black dome, the Dalek saucer commander was distinguished by alternating black-and-silver panels on the base unit. (TV: The Dalek Invasion of Earth)

A minority of bronze-type Daleks aboard the Dalek Emperor's flagship following the Last Great Time War had black base units with golden sense globes in addition to a black dome similar to that of the Emperor's Personal Guard. (TV: The Parting of the Ways)

Individual cases
Footage of a bronze Dalek's base unit and sense globes was captured by a British news broadcast during the Battle of Canary Wharf in 2007. (WC: Tardisode 13)

To complete the Empire State Building before the gamma radiation lightning strike hit Earth in 1930, three of the panels with sensor globes of Thay's base unit were removed and attached to the building's mast, as the Dalekanium of the plates was required to attract the gamma strike. In their place, Thay was given crude iron replacement plates. The Tenth Doctor attempted to remove them too late as the lightning struck him, resulting in Dalek-Humans infused with Dalek Sec's altered DNA as well as the Doctor's Time Lord DNA. (TV: Daleks in Manhattan/Evolution of the Daleks)

The bronze "Quasimodo Dalek", which was reconstructed by unfamiliar humans, had a base unit fitted with slats in place of the sense globes, which were here attached to the weapons platform and in place of the luminosity dischargers atop the dome. (COMIC: The Dalek Project)

Behind the scenes

 * This section is often referred to as the skirt.
 * 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 base units matching the colour of their wider casing; the Red Dalek had black sense globes, while the Black Dalek uniquely had a mix of silver and gold sense globes. Their subordinate Blue Daleks had silver base units with blue sense globes, similar to those from the contemporary TV serials.
 * In Daleks' Invasion Earth 2150 A.D., all Daleks have base units coloured according to their wider casings; the Gold Dalek has black sense globes, the Black Dalek gold, the Red Dalek has silver. The silver Daleks have blue sense globes, matching those from the contemporary TV serials.
 * In the video game The Last Dalek, based on the events of Dalek, the Metaltron gains the ability to ascend over stairs and manholes only after acquiring an anti-gravity device. It is further able to accelerate via the Speed Boost.
 * The "Dalek Patrol Ship" sets released in 2014 by Character Options included an exclusive 3.75-inch bronze "Dalek pilot" figurine bearing a black dome and alternating black "skirt" panels identical to the colour scheme of the Dalek saucer commander.
 * 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 base unit.