The Vehicle Bay or also referred as the "Large Printer", is one of the Tier-3 Modules in Astroneer. It is used to fabricate Vehicles and attachments for them. The Vehicle Bay needs 8 bars of Power to operate and 2x Aluminum to be built.
Tier 2 modules printed on a vehicle can be removed by hand, but Tier 3 modules are staying put.
When printing a Tier 3 module on a vehicle with the slots filled, the module will come off. This is useful if you want a storage to put all your Medium Storages on.