I had wondered how Stamping Mathilda created her unusual folded cards. First I had to find out what size an A4 sheet of paper was... to the web! An A4 card is 210 × 297 mm, which is about 8.2677" X 11.69289" - so we can use an 8 1/2" X 11" sheet of paper... we Americans. Stamping Mathilda has a bit more paper to create with. I had to make a card today... couldn't wait.
Stamping Mathilda's Instructions: (my liberal spray of words in blue)
Fold in half on the 8 1/2" side so you have two long cards, not the way I would normally cut to make a notecard. I hope that makes sense. Cut in half, you have two folded cards now, which fit in a regular envelope and indeed they do. Score at 10,5 cm... that's 4.1 inches... You can decorate the narrow part (stamp, emboss, punch,...). You have to see how many ways she has used this card - like a shaker card, embossing and glueing shut... go check it out at Stamping Mathilda.