When coupling together two trailers, you can secure the second trailer by:
If you are attaching a second trailer to a combination but the trailer is not equipped with spring brakes, you can set the trailer emergency brakes. You can do this by connecting the first and second trailers' emergency lines, charging the air tank, then disconnecting the emergency lines. This should set the emergency brakes, as long as the slack adjusters are properly adjusted.
This questions appears in the following tests:
