Add a rapid-fire button to your mouse using a 555 timer

Step 4 Mount the switch to the mouse.

Mark a location for the switch in the side of the mouse. You want it where your thumb has easy access to it. Since I'm left-handed, I put the hole on the right side of the mouse. Either drill a hole, or use your soldering iron to burn a hole through (I do not recommend this method if you respect your soldering iron!)

Use epoxy or hot glue to hold the switch in place permanently.

Once the glue is cured, and the wires are connected, reassemble the mouse, making sure that the 555 circuit doesn't short anything out, and vice-versa. If you choose, wrap the 555 circuit in tape to prevent shorting things with it.