Envelopes and paper products are sized in accordance with guidelines from the International Standards Organization. The ISO sets worldwide standards for almost all products so that shipping from one nation to another goes smoothly. A5 paper is the perfect size for invitations and handmade cards. It measures 148mm by 210mm, or 5.83 inches by 8.27 inches. When folded in half for mailing, it needs an envelope measuring 6 by 4.25 inches.
Place the A5 note in the centre of the paper and lightly mark the edges of the note with pencil. Remove the note.
Place a ruler at one pencil mark, and fold the paper in toward the centre over the ruler's edge. Run your finger across the paper as it is upright to ensure a crisp crease.
Move to the next pencil mark and repeat folding edges in until all are creased. Unfold paper; you should have two vertical and two horizontal creases.
Cut off the four rectangular pieces in each corner
Measure 3/4 of an inch in from both the left and right edges of each flap and mark with pencil. You should have eight pencil marks.
Cut from the pencil mark toward the nearest corner of each flap, removing two triangular pieces from opposite ends of each flap.
With the paper horizontal, fold the left and right flaps in. Make a crisp fold by running your fingernail over the folded edge.
With a pencil, draw a line on the left folded flap 1/2 inch in from the centre and bottom edge of the flap. The centre pencil line should begin two inches up from the bottom crease. Repeat on the right flap, which should look like a mirror image of the left flap. These mark the glue area.
On the bottom flap, draw a 1/2 inch line along the left and right slanted inside edges, then extend the lines one inch parallel to the bottom edge. This marks the bottom flap glue area.
Apply glue to the inside flaps; fold the bottom flap up and press all glued areas firmly.
Insert the note in the envelope and run a 1/2 inch line of glue across the bottom edge of the top flap. Seal.