| 摘要 |
<p>The envelope is rectangular in shape and has two parallel sheets of transparent plastic. The rear sheet of plastic is longer than the front sheet. The rear sheet is fitted at the top with a permanent magnet which extends over the entire width of the envelope. The front envelope is independent of the magnet at the top, being joined to the back sheet. The bottom of the front sheet also has a permanent magnet which extends across the width of the sheet. The documents or drawings are inserted between the sheets. The envelope may be fixed to a metal surface. If the bottom magnet is lifted, the drawing may be removed.</p> |
