| 摘要 |
<p>The envelope is made up of four flaps folded over from the front. Three of the flaps are permanently glued down, and the fourth is opened until the envelope is sealed. The inner edge of the flap (1) has spots of gum. When the envelope is closed by folding along the edge (3), pressure on the envelope will allow the air in the envelope to vent through the ungummed portions of the flap, and reduce the thickness of the envelope for handling by automatic sorting or franking machinery.</p> |
