Envelopes are a part of most of our day-to-day lives, from sending and receiving bills to sending and receiving gifts, personal letters and greeting cards. While most envelopes require you to fold whatever is going in them, sometimes the need arises for correspondence to be sent lying flat; i.e., official documents or larger photographs. The perfect way to send mail without folding it is to make an A4 sized envelope.
Lay the A4-sized paper in the middle of the A3-sized paper, and trace around the edge of the A4 with the pencil. Remove the A4 paper.
Rule a line all the way around the A4-sized pencil line. Be sure that it is 6 mm (1/4 inch) larger than A4.
Rule another line all the way around three sides of the rectangle, 2.5 cm (1 inch) from the previous line. Be sure that one end has a line that is 5 cm (2 inches) away from the previous line, this will be used as the closing tab of the envelope.
Draw a line between each corner of the original ruled rectangle, and the outer ruled rectangle, at an inward angle of about 20 degrees off 90.
Cut around the outline of the outer rectangle, including the angled lines meeting the points of the inner rectangle.
Fold the side tabs inward on the inner rectangle line. Leave the 5 cm (2 inch) tab unfolded for now.
Place a line of glue on the very edge of the A4 piece of paper leaving one end with no glue, which will match up with the 5 cm (2 inch) tab.
Center the A4 paper over the folded tabs, pressing it down so that it glues to the tabs, with about 6 mm (1/4 inch) space on every side. Make sure the side without glue is facing the 5 cm (2 inch) tab, to leave an opening. Let dry.
Fold the 5 cm (2 inch) closing tab on the line. The envelope is ready for use.