Because when the stapler hits nails, there is an iron sheet on it to hold down the staples. If the nails are uneven, it will lead to uneven stress on the nails and make them offset, so they cannot be nailed.

Introduction to the invention:

The traditional book binding method is to sew the pages together according to the label. This is a rather complicated process, which is simple for skilled bookbinding workers, but it may be difficult to do it with machines. Therefore, bookbinding workers who want to improve their working speed, especially when making brochures and magazines that usually require high speed, are trying to bind them with small pieces of bent iron wire.

Historical evolution:

1869, Thomas Briggs of Boston, Massachusetts invented a machine that could do the job. He set up a "Boston Wire Binding Machine Company" to manufacture and sell this machine.

His machine breaks the wire and bends it into a U-shape, then uses it to nail through the pages, and finally bends it to fix the book correctly. Briggs' original stapler was quite complicated because it had many steps.

1894, he adopted a manufacturing process. First, the iron wire was bent to make a series of U-shaped staples. These nails can be put into a simpler machine, which can embed them into paper. This machine is the prototype of today's stapler. Early U-shaped nails were wrapped in paper or put in a stapler alone.

Staplers were widely used in the 1920s, when U-shaped nails could be glued into a long strip and put on the market.