Flip the card over on your scoreboard and score along the card as if you were making a fold for an A6 card (at around 73-74mm) this will divide the card into quarters .
Rotate the card and repeat another fold on the other side and using a bone folder fold back the creases on the score lines to create a tall concertina card.
This creates two little basic concertina cards all ready for working on!
As these can be quite bulky I tend to store and pass these on partly unfolded in a basic size A6 envelope.
I do hope my waffle makes a little sense!