|This article is about a form in Kamen Rider Zi-O.|
|"(Ziku-Driver D '9 Slot Ridewatch's transformation announcement)! Armor Time! Best Match! Build!"|
|"(King) Finish Time! Build! Vortex (Barlckxs/Zonjis/Zamonas) Time (Break/Burst/Jack)!"|
BuildArmor (ビルドアーマー, BirudoĀmā) is a Kamen Rider Build-based form accessed using the Build Ridewatch, invoking Kamen Rider Build's RabbitTank Form and wielding the Drill Crusher Crusher (ドリルクラッシャークラッシャー, Doriru Kurasshā Kurasshā). When summoned, it is projected in a holographic Fullbottle and does Build's signature pose before dispersing to attach to the user. BuildArmor's Fullbottle Shoulders (フルボトルショルダー, Furubotoru Shorudā) are modelled after Empty Bottles, and depending on whether it is used by Zi-O or Geiz, its visor spells out "Build" (ビルド, Birudo) in katakana or "Build" (びるど, Birudo) in hiragana respectively.
|"The laws of victory—"|
"—have been set!"
|―Sougo Tokiwa attempting to channel Sento Kiryu[src]|
Encroaching on a battle between the first eighteen Heisei Riders and numerous monsters, Sougo Tokiwa assumed the BuildArmor before proceeding to seemingly wipe out all combatants. This act was witnessed by Sento Kiryu, the original Kamen Rider Build, who had been transported to the same location as a result of experiments he had conducted with the White Pandora Panel.
During Another Build's attack on Kamen Rider Build and Cross-Z in 2017, Sougo used the Build Ridewatch given to him by Sento's future self to try to protect the timeline and defeated Another Build. But as a side effect, Sento reverted mentally to Takumi Katsuragi and his powers were erased from time.
On September 17th, Zi-O assumed the BuildArmor to fight alongside Geiz DriveArmor against Another Ex-Aid. Soon after, Zi-O performed the Vortex Time Break alongside Geiz's Time Burst to defeat Another Ex-Aid. However, it was at that point that Emu Hojo arrived and transformed into Kamen Rider Ex-Aid Action Gamer Level 2, proceeding to attack Zi-O and Geiz. The fight was interrupted when the Time Jacker Ora arrived and, having paused time, refreshed Ida's Ridewatch and allowed him to become Another Ex-Aid, resulting in Emu losing his Kamen Rider identity and associated memories as Another Ex-Aid ejected all parties from the Game Area.
On October 5th, during a fight against Another Fourze, Sougo dropped the Build RideWatch when he attempted to activate it. But, before he could use it, Geiz snatched it and activated his version of the BuildArmor. After the fight, Geiz gave the RideWatch back to Sougo.
On October 21st, Zi-O assumed the BuildArmor and performed the Vortex Time Break to temporarily neutralize Another Wizard, causing Kosuke Nitoh to briefly regain his memories of fighting alongside the original Kamen Rider Wizard as Kamen Rider Beast.
On October 27th, Sougo used the BuildArmor when he was challenged by Geiz, outraged at his decision to follow Kuroto Dan as a member of the Dan Foundation. Having grown experienced as both Zi-O and in the BuildArmor, Sougo was able to overwhelm Geiz's default Rider form before performing the Vortex Time Break to defeat him as Geiz was forced out of his transformation.
Following the appearance of Another Quiz, Geiz, intending to defeat the Another Rider without erasing the memory of Kamen Rider Quiz, clashed with Zi-O. In a battle mirroring their prior confrontation, Geiz assumed BuildArmor and performed the Vortex Time Burst to force Sougo out of his transformation.
Facing a second Another Build, Zi-O assumed BuildArmor and performed the Vortex Time Break to defeat Another Build, only for the Another Rider to immediately switch to the form of Another Ex-Aid, proceeding to overwhelm Zi-O. Seeing Sougo in a pinch, Woz spirited him away to safety.
|"(Digital beeping) Build!"|
|"Best Match! The genius Rider who transforms with Fullbottles is... (Clock ticking noise) Build! (ベストマッチ！フルボトルで変身する天才ライダーは…ビルドだ！, Besuto Matchi! Furubotoru de henshin suru tensai Raidā wa… Birudo da!)"|
|―Secondary activation announcement[src]|
|"Rider Time! (RabbitTank-esque rock music) Best Match! Build!"|
|―Transformation announcement in the Ziku-Driver's right-hand slot[src]|
|"(Right-hand Ridewatch's announcement)! Armor Time! (RabbitTank-esque rock music) Best Match! Build!"|
|―Rider Armor transformation announcement[src]|
Build Ridewatch (ビルドライドウォッチ, Birudo Raidowotchi): Based on Kamen Rider Build RabbitTank Form, this Ridewatch provides access to the BuildArmor. It is dated 2017.
- Vortex Time Burst (ボルテックタイムバースト, Borutekku Taimu Bāsuto): which has two variations:
- Rider Kick: Geiz performs Build RabbitTank Form's Vortex Finish Rider Kick; creating a white energy chart flying up to the surface with the dotted line securing the enemy before leaping back up and delivering a Rider Kick whilst riding the chart's line.
- Rider Thrust: Geiz performs a variation of the Zi-O's Vortex Time Break, that has the energy chart occupy a straight line he slides on and stabs the enemy with the Drill Crusher Crusher.
- Kamen Rider Build: Be The One
- Kamen Rider Zi-O
- Another Build (Another Rider) - The result of using the Another Build Watch