Dear all.
I am looking for a recommended way (and perhaps a practical one too) to join side by side 2x Timber Lining Boards Easy VJ100 using provided green tongue & groove.
With 1200 mm vertical length, it is a quite challenge to do insertion tongue into another groove vertically (particular when one of the board has been nailed to the wall side).
I also tried to do insertion by pushing it horizontally. It was hard to push the tongue into another groove due tongue width is slightly bigger than the opening size of the groove. I guessed that is how the design idea, to prevent 2 joined boards separated horizontally using tongue and groove mechanism.
vs. 
Thank you for all of your advice.
Regards,
Daniel