What we need

You will need:

• Sewing thread and a needle, or two safety pins.
• Some cotton fabric
• Elastics (standard adult length: 17cm / 6.7in)
• 1 iron

If you don't have elastic bands, you can cut a length out of an old t-shirt or leggings. The cut part should be sufficiently elastic.

When choosing a cotton fabric, it's important to check that the threads that compose it are tight enough to act as a barrier.

A simple and efficient test is to observe if the sunlight is passing through it. If a lot of light passes through, then select a fabric which seems more opaque to it, because the meshes that compose it are tighter.