You will need:
Card
Pen
Ruler
Scissors 

Use your pen and ruler to mark the card into strips of 12cm x 4cm and carefully cut these out.  You may need to ask an adult for help. 

Mark a line at 4cm and 8cm along the strips. 

Fold along the marks and tape the strips to make triangles.

Start building!  Try putting 3 triangles in a row and lay a strip of cardboard on top.  Now build another layer with 2 triangles and a strip of card.

What can you put on top?  Can you build a bigger tower?  Why is it so strong?