"Future Trunks: Let my strength be a shield. For this world, and for all of humanity! I'm putting all of our hopes into this one blast!
It was formed when the two users stood side by side and both fired a Galick Gun together. They were close enough that the two blasts combined into one giant blast.
Usage and Power
This technique was first used to counter Fused Zamasu's Holy Wrath. At first, Future Trunks just fired off a single Galick Gun, but then Vegeta joined him and fired his Super Galick Gun as well. They were so close that the two Galick Gun blasts combined into a bigger blast and was strong enough to overwhelm Fused Zamasu's attack.
Video Game Appearances
A similar attack is used by Vegeta with his younger brother Tarble called the Brotherhood Galick Gun, which also appears in Dokkan Battle as Tarble's super attack.