Easy To Open Creative Envelopes

Nearly half of the estimated 450 billion envelopes made each year worldwide are machine-made.
• History of envelopes
Prior to 1845, hand-made envelopes were all that were available for use, both commercial and domestic. In 1845, Edwin Hill and Warren De La Rue were granted a British patent for the first envelope-making machine.
The "envelopes" produced by the Hill/De La Rue machine were not as we know them today. They were flat diamond, lozenge (or rhombus)-shaped sheets or "blanks" which had been precut to shape before being fed to the machine for creasing and made ready for folding to form a rectangular enclosure. The edges of the overlapping flaps treated with a paste or adhesive and the method of securing the envelope or wrapper was a user choice. The symmetrical flap arrangement meant that it could be held together with a single wax seal at the apex of the topmost flap. (That the flaps of an envelope can be held together by applying a seal at a single point is a classic design feature of an envelope).