The Vault (or Dosh Vault) is a feature in Killing Floor 2 allowing players to accrue a new form of Dosh by completing Daily Objectives and Weekly Outbreaks, going Prestige on a Perk, as well as receiving a small amount after each match.
This new Dosh (called Vault Dosh or Vosh) is visually shown as accruing onto large palates in an empty warehouse accessible from the Main Menu. For every 500,000 Vosh earned the player is rewarded with a Vault Crate containing a non-tradable, non-marketable cosmetic gear or weapon skin.
Every cosmetic earned from the vault will bear the identifier “Vault” in the item title. These can also be recycled for crafting material that can be used for another chance at a Vault item. Unlike other crafting materials, you only need two instead of ten to craft a new item (actually 1.5, but the game doesn't display decimal points).
The Dosh Vault was introduced in the Halloween Horrors update in October 2017.