This property determines whether an Instance|object should be included when the game is published or saved, or when Instance/Clone is called on one of the object’s ancestors. Calling Clone directly on an object will return nil if the cloned object is not archivable. Copying an object in Studio (using the ‘Duplicate’ or ‘Copy’ options) will ignore the Archivable property and set Archivable to true for the copy.

local part = Instance.new("Part")
print(part:Clone()) --> Part
part.Archivable = false
print(part:Clone()) --> nil