Here's how to draw straight lines without a ruler - by doing them bit by bit.

You will need:
  • Paper
  • Pen
Here's a part-finished picture.

The train in the picture needs a bridge to get across the gorge!
Instead of drawing one long straight line, draw the line bit by bit, using little lines.
Draw a short line, and then extend it a bit...
...and keep pushing it out, further and further.
Every now and then, stop to check that it looks OK.
When you're happy with the line, go over it again.
With a bit of practice you'll be able to draw any long lines by doing small lines and extending them bit by bit.
You can use a similar technique for shorter straight lines.

Do them really quickly with a flick of the wrist.
Neil used a combination of both techniques to finish the top part of the bridge off.

Try it yourself!