# A Rectangular Tetrahedron

Once you know how, this is a simple project - turning a flat rectangular piece of paper into a full tetrahedral solid.
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## Step 1: Thirty-Six by Five

That's the secret - you need a rectangular piece of paper or light card with sides in the ration of 36:5.

It can be 36cm x 5cm, 9" x 1.25", whichever you like. Obviously, the larger the piece of paper, the larger the model you can make. You can, if you want, use two pieces that are in the ratio of 18:5, then tape them end-to-end to make a larger piece*.

If you have some sort of graph paper, your job will be made a lot easier, because all you need to do is count squares.

* The next steps will assume you are using a single, long piece of paper, but if you've got the brains to check this footnote, you're able to adapt the instructions to using two separate pieces.

## Step 2: Preparation

Draw dotted lines to divide the length of the rectangle into four equal parts. If you are using a piece that is "36 squares" long, then each section will be "9 squares" long.

Draw another dotted line from corner-to-corner of each of the smaller rectangles. Pay attention to the images below - they must alternate in direction, so your paper looks like a pair of broad arrow-heads.

Carefully crease along each dotted line, both valley and mountain fold, so that the paper bends easily both ways.
Kite builder7 months ago

I know this, a friend of my famely gave me a redy one

Spycrab5 years ago
sweet! going to make an army of these to unleash on. . .my..er..any volunteers? :-]
chriskarr5 years ago
It will also work, like with most paper (in America, at least) with 11" X 1.528". With any given length of paper, all you have to do is take the length and multiply it by the result (different calculators will give different results) of the equation 5/36. My calculator gave me 0.13888888888888888888888888888889 which I then multiplied my length, 11", by; 0.13888888888888888888888888888889*11, my calculator gave me 1.5277777777777777777777777777778 There you are, my own formula (and probably the one in use by Kiteman) for finding Kiteman's magical tetrahedron length:height ratio.
PKTraceur6 years ago
Schweet! d4!
knexfan91826 years ago
thats cool i might make it. +5*
Kiteman (author)  knexfan91826 years ago
Thanks!
6 years ago
np I'm gonna make it after i clean my room tomorrow. *ps do you want before and after pics of my room lol its kind hard to walk in there atm.*
Kiteman (author)  knexfan91826 years ago
LOL, sounds like my youngest's room.
6 years ago
hmm how much of the year can he/she walk in it with out stepping on something?
Kiteman (author)  knexfan91826 years ago
6 years ago
i knew you liked D&D >:D
6 years ago
YEA HA!
iectyx3c6 years ago
This is great. It works because 9 is very close to the actual value of 8.66 for a regular tetrahedron. And the way it can store flat in your wallet is very cool. Nice Instructable and fun to play with.
Kiteman (author)  iectyx3c6 years ago
If you use public transport, try sitting on the bus and taking one of these out of your pocket, flat. Play with it a few times and then hand it to anybody who was pretending not to watch you.

Then watch everybody else watch them. Priceless.
=SMART=6 years ago
Here is My Tetrahedron, I made the larger size and drew it out by hand. Cool instructable 5*
Kiteman (author)  =SMART=6 years ago
Very nice - well photographed as well.
6 years ago
Thanks :P, I turned my screen off to use as a black background, but for some reason my fingers are really white in the 3rd pic ?:P
Kiteman (author)  =SMART=6 years ago
Washed out by camera-flash?
6 years ago
Probbaly
6 years ago
Or you're just nerdier than you think you are 8-)
gmjhowe6 years ago
nice, good job!
=SMART=6 years ago
I added this to the Papercraft Group too :D
Kiteman (author)  =SMART=6 years ago
Oh? That's fine.
=SMART=6 years ago
Haha very nice, mines printing now :P Looks cool, and good pictures
Kiteman (author)  =SMART=6 years ago
Thank you, but you could have just drawn it, like I did. (I made the image in step 1 by using Corel to draw over a scan of the hand-drawn rectangle I use in the photos).
LinuxH4x0r6 years ago
*golf clap* Very nice!
Kiteman (author)  LinuxH4x0r6 years ago
Thank you, but what is a "golf clap", anyway?
6 years ago
It's a very polite, quiet clap (because we wouldn't want to break the golfer's concentration!). I don't think he meant it rude.
Kiteman (author)  Lithium Rain6 years ago
Oh! Jake Tobak's link said it was sarcastic, like a slow clap.

Sorry Linux.

(Climbs down off high horse.)
6 years ago
No, just polite and quiet-kinda like the British. Ducks head
6 years ago
WWWWWHHHHAHAAATTTTTTTT!?!?!?!?!?!? lol
Kiteman (author)  LinuxH4x0r6 years ago
OK, now I know what a golf clap is, what is your problem with the 'ible?
6 years ago
No problem. I didn't know it was sarcastic. I liked it. I have no clue why. tired. go away. stop asking hard questions
smheath6 years ago
You mean 9" x 1.25".
Kiteman (author)  smheath6 years ago
Oops, thanks for catching that!
Kiteman (author)  Kiteman6 years ago
Fixed.