The Tetrad Corner

What is a tedrad? Tetrads are all of the shapes you can make with 4 blocks. You are probably familiar with them from playing the game Tetris. If you would like to know more about them, see Wikipedia: Tetrad

What is this page? This is a silly page to show you some things that can be done with tetrads. If you have an idea for this page, please email it.

Use tetrad-shaped passwords on your phone

Phone passwords are often 4 digits, and tetrads have 4 blocks. This tool will choose a 4-digit number which forms the shape of a tetrad on a standard phone keypad. There aren't many possibilities, so don't use one of these for anything important!

Random password:


Reloading the page will generate a new password.

Make tetrads out of paper

Nets for constructing tetrads
I have put together nets for every possible tetrad in two dimensions, so that you can construct them out of paper. Download the nets here (PDF, 32.9kb).


  1. Print out the PDF file. Use thin card or something colourful if you have it.
  2. Cut out all of the outside edges of the shapes, and fold every line
  3. Use your geometry skills (and a glue stick) to stick down all of the tabs.

Fill a box with tetrads

This will pack some tetrads into a box for you. The filler script page will let you make your own.

Write PHP scripts with tetrads

The source code to my tetrad class for PHP can be found here.

Use tetrads on a web-page

These generated HTML tables are the same as the tetrads shown on this page. You will also need tetrad.css to style these on your web-page.