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!