In just a few seconds, your national number can be permanently engraved on your bicycle frame. Thieves will avoid nicking your two-wheeler because it won't be easy to sell. And even if someone were to steal it, you would have a far better chance of getting it back. On a practical note, you should know that the engraver doesn't work on curved frames. Don't forget your ID either.
Where to engrave your bike in Brussels
You can give your bike a personal tattoo for free from Monday to Friday between 7 am and 7 pm at the points vélo in big train stations: Norht, Central, South, and Luxembourg. CyCLO offers the same service from Tuesday to Saturday in their workshop on rue de Flandre. Depending on the workshop's availability, your bike will be engraved within 24 hours (if not immediately).
Head to Pro Velo on Wednesdays. You will be asked for 2€ for this service.
Despite these precautions, there is still a chance that your bike will make a quick exit. Consult www.velosretrouves.be. You can set up an email alert for when your bike is found. And if you haven't gotten it engraved, you can still peruse the picture of bikes found on the site.