How to draw a rectangle of 1m by 0.5m in practice?

Question

I have my whole school stuff to draw a rectangle of 20cm by 10cm, but seriously I want to draw on a cardboard a rectangle of 1m by 50cm, and any small deviation gives quickly several cms of error at the end...

Of course I'm not looking for solutions who require to buy any ruler/compass/protractor of 1m length.

Answer 1

You could use a cord with pencils at each end for a ruler of arbitrary length. For constructing a right angle, either use a big object with a right angle, like a book, or use a (small) compass to construct it.