Padlocks are a wonderful invention. They're cheap, they're moderately effective, and they can be used on almost everything, from doors to suitcases to containers. There are only two minor caveats regarding padlocks: don't lose the key, and don't lose the padlock.
Limit #28 Open All The Locks
Losing the padlock will leave the property accessible for anybody, and depending on the area where you live this could be quite disastrous.