3rd container tier. Short lashing bars, about 2500 mm long are for insertion into the corner casting at the bottom of the 2nd tier of containers.
Turnbuckles have a maximum and minimum opening length. If you turn the bars of the turnbuckle they will tighten or loosen depending on the direction turned. During container use, you want the turnbuckle to have all slack taken out of the system, but you dont want the fitting to be too tight. Hand tight is plenty.