Many of you are probably not wondering: HAL, what did you do when you forgot to get one of your two friends a christmas present? Well, since he is into bluegrass guitar, I gave him one of these, which he mistook for a piece of broken glass.
This is how to make your own professional-seeming glass guitar slide from a bottle to get that nice bluesy sound, or to play any number of other types of music. This is a very easy method of making a great tool for guitarists, and makes great, cheap gifts for your guitarist friends.

Step 1: Gather Materials

For this project you will need a few materials and tools. These are:

One bottle. This should have a very pronounced neck, unlike some beer bottles which just taper slightly to the top. The project will work best if the neck on your bottle has a long, straight section, like a wine bottle.

Glass Cutter. If you don't have one, get one. I got mine for i think $3.50 at the hardware store, and its very useful if you're into DIY. This is essential to the project.

Sandpaper. You could rub the glass on the wet sidewalk, this also works. I use a combination, since the sidewalk is rougher than my sandpaper.

You may also want gloves, since there is a guaranteed potential for broken glass. hearing protection is also advised, since there is also a potential for loud noises.

Step 2: Cut Around the Neck

In this step we will cut the bottleneck, which will become the slide. for this you need to know how to use a glass cutter.

A glass cutter does not actually cut glass, rather it scores a "weakest link" line into the glass which, when the glass is broken, will redirect the direction of the breaking along the scoring line.

To use your glass cutter score a line around the neck applying pressure with the cutting wheel along the glass, like in the picture. Try to make just one, straight line to get a good, clean cut.

Step 3: Smash Your Bottle

Now it's time smash your bottle. Grasp firmly by the neck, and swing the bottom of the bottle into something solid. This should not be something breakable, or something that you don't want small shards of glass on/in. I have always used the can we collect our glass bottles in as a receptacle, and it has worked quite well.
I have never actually shattered a bottle into pieces, there is a mostly clean break on the line. There are some very small fragments that will come off, smash it in something that will collect the pieces. There is also a chance that the bottle with shatter, so this is where you would want gloves and hearing protection. Broken glass specializes in cutting through flesh.

If you have cut it properly you will be left with a small tube of glass in your hands, but be careful, there will be one very sharp edge on the part which was until recently happily connected to the rest of the bottle. We take care of this mangler in the next step.

Step 4: Smooth Out the Edges

Now you basically have a lovingly crafted weapon suitable for a prison/barroom fight. If you want this, set it aside, start over and continue with what will be your slide. It's time to get rid of the sharp edge.

You may wish to wear gloves for this as well.

Scrape the edge of your bottleneck on some smooth pavement. It will help it it's wet. Grind it at different angles to round out the broken edge until you can see that it is no longer sharp. If you wish to get a smoother edge, proceed to sandpaper and smooth as much as you like.

If you don't have access to some smooth pavement use sandpaper, since it works just as well, but not as quickly. Sand inside and out, leave no sharp cutting edges.

I prefer the rougher look and I only use sandpaper on the inside of the edge. I'm sure if you worked your way to finer sandpaper and polished, perhaps with a Dremel tool, you could get a nice, factory-looking edge on it. Since this is homemade, I'm fine with the homemade look.

Step 5: Play Some Delta Blues

If you have no idea what you're doing, slides sound great on acoustic guitars. It's a fun way to get a nice bluesy sound, though slides are also found in country-western music and many other types. And even if you don't play, they make great gifts!
Now, Practice, Practice, Practice. Just slide it onto any finger (you'll develop a personal preference) of your fret hand and place it over the strings. Apply pressure enough to stop the string vibrations, but don't press the strings against the frets. Slide up and down the strings as you pick or strum.
Maybe i will make a future instructable on tuning and playing with a slide, but for now I'm still playing around with it. I have found that playing with the slide on my ring finger allows me to use my first and second fingers to dampen the portions of the string behind the slide, blocking out the weird, harmonic-like sounds i get otherwise. Remember, the slide doesn't go where your fingers go, it goes directly over whichever fret produces the desired note.

I hope you all have enjoyed this instructable, please rate, comment, and of course, try this one out for yourself.

And remember, if the women don't find you handsome, they should at least find you handy.