As part of a series on planning your European backpacking trip, we're taking a look at a few things you need to know, do and get before you go and when you get there.
You're unlikely to have your entire backpack 
stolen from your side while traveling across Europe (too big to be spirited quickly away), but thieves can reach right in if you leave your pack while walking the street -- avoid that by threading small, inexpensive but tough-enough TSA-approved luggage locks through two meeting backpack zipper pulls. You need locks like these for US airport security on your return, anyway (find out why); carry three luggage locks to Europe -- one for main pack and one for day pack, and one for a hostel locker. Hostels typically charge to rent locks for provided lockers, and bringing a Master-type lock like you used on a school locker backfires twice: it's very heavy (every ounce counts when you're hauling everything) and it may be too big for hostel lockers (some whacky lockers may require rental locks, though). These locks may seem small, but they'd have to be clipped off before you can be ripped off.
Related backpacking Europe tips: Travel Foot Notes | Top Tips for Travel Cash Stashing | Backpacking Europe 101
Similar stuff: Student Travel Safety | European Train Safety | Women's Travel Tips
stolen from your side while traveling across Europe (too big to be spirited quickly away), but thieves can reach right in if you leave your pack while walking the street -- avoid that by threading small, inexpensive but tough-enough TSA-approved luggage locks through two meeting backpack zipper pulls. You need locks like these for US airport security on your return, anyway (find out why); carry three luggage locks to Europe -- one for main pack and one for day pack, and one for a hostel locker. Hostels typically charge to rent locks for provided lockers, and bringing a Master-type lock like you used on a school locker backfires twice: it's very heavy (every ounce counts when you're hauling everything) and it may be too big for hostel lockers (some whacky lockers may require rental locks, though). These locks may seem small, but they'd have to be clipped off before you can be ripped off.
Related backpacking Europe tips: Travel Foot Notes | Top Tips for Travel Cash Stashing | Backpacking Europe 101
Similar stuff: Student Travel Safety | European Train Safety | Women's Travel Tips
If you are worried about safety, you could always go with Big Brother Backpacking (http://www.bigbrotherbackpacking.com). They specialize in providing students with adventure tours across Europe, without the worry that accompanies sending your teen to a foreign continent. Since their tour guides let the student travelers make the decisions on destinations in real-time and no tour group is larger than five members, it is essentially the same as backpacking with a small group of close friends.
Plus, with a guide nearby twenty four hours a day, there is no need to worry about the safety of your things.
I wouldn’t advise anyone to use the 4-dial combo lock (as pictured on the bottom-right). It’s WAY too easy to crack these. Your Grandma Betsy could crack one of these locks in less than 90 seconds.