TSA Locks were developed for travelling from and to the US. Since 9/11 US TSA agents (Transportation Security Administration) are allowed to open all luggage even if they have to break padlocks and locks.
Whilst current technology allows them to screen luggage there are time's when they need to physically open cases. This will be done without consulting the passenger, you will be notified with a letter placed in your suitcase.
If you are concerned about damage to your suitcase you have two options, either leave your suitcase unlocked or fit it with a TSA approved lock.
A TSA lock can either be a combination or key lock but it also carries an additional lock which can be opened and relocked by a TSA agent without damaging your bag. Some locks also have an indicator that will tell you if your suitcase has been opened.
In the UK whilst there are not as many spot checks as in the US, TSA locks are still accepted and can be opened and relocked by UK Custom officials.