This is an easy way to make a shofar horn that actually works. To hear the sound of the cardboard shofar, go here: https://www.youtube.com/watch?v=_4P2ciyPPcU

All you need are:
Scissors
Ruler
Marker
Pen
Hot glue and gun
Thin cardboard

Step 1: Open the Box

Take a large box and open the box at the seam.

Step 2: Measure and Draw

Once the box is fully opened draw a diagonal line across. Then make the next line one quarter width apart at the top and three quarters width apart at the bottom. Cut just inside the line so the lines don't show. The cutout peice will look like a tie shape.

Step 3: Curling

First you will need to use the marker and press down on the cardboard as though you are curling a ribbon. This prepares it to be curled into shape.

Step 4: Curling Part 2

Now take the market and curl the cardboard around it. A nice thick market like a highlighter will work just fine.

Step 5: Making the Shape

Stretch out the curled cardboard to the shape of the shofar that you would like. *Note the more curved you make the horn, the higher the pitch and the more elongated you make it the lower the pitch. I'm much more fond of the lower pitch.

It is very important to make the mouth piece 1/2 inch inner diameter or you will not be able to blow to make a sound. Also, as you wrap around and glue, you want to make sure that you make pentagon shapes between each wrap around in order for it to curve. It will need some curvature in order to play properly. Please look at the pictures carefully to better see how to glue the shofar together.

Step 6: Cleaning It Up

Any glue that is sticking out can be simply melted with the tip of the hot glue gun and smeared flat. This gives it a better overall appearance.

Step 7: Sealing the Mouthpiece

This step is one that should not be skipped if you want to be able to use your shofar longer than a week. Add glue to the inside and outside of the mouthpiece and smear it all around. This will seal the cardboard from any water/spit damage.

Step 8: Add Decorations and Enjoy

Use the hot glue to add a menorah or any other decoration you like. I like to keep mine the brown color to keep it more organic, but feel free to add color too. Outer decorations do not affect the sound of the shofar.

Now your ready for Yom Teruah!