A stapler is an office tool that is used to place thin items such as paper together. It uses a small piece of wire (a staple) to put them together. The ends of the staple are pointed and go into the paper. There is also a chain of stores called Staples, which sell office supplies.
When you press the stapler down, it will release a staple. The staple is pressed into the paper, and then bent. That way the pieces of paper get stuck together.
An office stapler
This stapler can also put together bigger things
Staple fasteners (before use)
Staple fasteners (after use)