When you try to write with it, it will let out an annoying beep, and chances are, no one will know where it is coming from!
This is a project I thought of while in math class. I hope you have as much fun making and using it as I did!

Step 1: Parts

First, you need to gather your parts. Get your hands on a whiteboard marker, a piezoelectric buzzer, a AA battery and a mini tactile switch.

Step 2: Supplies

In order to assemble the pen, you will need some wire (fairly small gauge) and some solder. Flux is optional but I recommend having it on hand.

Step 3: Tools

Get your tools ready! You need a set of wire strippers, wire snips, needle nose pliers and not shown but the most critical tool, a soldering iron.

Step 4: Step 1

Remove the back cap from the marker to access the inside with your pliers
Then use your pliers to remove the ink cartridge from inside the maker (you can toss this.)
And finally, extract the felt tip and hold on to that for later.

Step 5: Step 2

Now you need to dry out the felt tip so that it will shrink and slide freely in the tip. I found that the most efficient way to do this was wrap it in a paper towel and microwave it for about a minute. Then flip it around and cut off the least frayed end.

Step 6: Step 3

Now cut a piece of wire about 3 1/4" long and strip 1/8" from each end.

Step 7: Step 4

This is where you really need to pay attention. Begin by cutting two pins off of the button diagonal to each other THE LONG WAY, and then bend one lead up so that is is parallel to the bottom of the button. Now solder the lead that is congruent to the bottom of the button to the POSITIVE terminal of the battery and bend is down to be flush with the positive terminal. Next, bend one end of your wire to a 45 degree angle and tape it to the battery. Finally, solder the wire to the other pin on the button.

Step 8: Step 5

Now we focus on the most important component, the piezoelectric buzzer. Melt a glob of solder to the negative terminal of the battery, and while it is still molten, attach the NEGATIVE lead of the buzzer to the negative terminal on the battery. Then solder the other end of the wire to the POSITIVE lead of the buzzer. Congratulations! The hard part is over! You are nearly done!

Step 9: Step 6

Now all you have to do is slide the whole assembly into the marker with the button facing the writing side of the pen, slide in the felt tip and replace the back cap!