Why a stapler bends the staple underneath
A stapler does two jobs in one press: it drives a staple through the paper, then bends the projecting legs against a shaped metal plate underneath. Those folded legs hold the sheets together. Without the plate guiding that bend, the staple would mainly leave two straight points sticking out.
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Piercing first, folding second
Inside a typical desk stapler, a spring pushes a row of staples towards the front. Pressing the handle moves a driver blade down onto the leading staple.
The driver forces the staple's two legs through the paper. Underneath, a metal plate called the anvil has shaped grooves. As the legs meet these grooves, they are guided into bends that secure the sheets.
The paper is held between the staple's upper bar and its folded legs. The useful fastening action therefore depends on both the driver above and the anvil below.
- The magazine stores and feeds staples.
- The driver pushes one staple through.
- The anvil shapes the protruding legs.
Some staplers have a reversible anvil that changes the direction of the bend. A stack that is too thick can leave too little staple length available to form a secure fold.