How damage-free opening works
Locksmiths use professional lock-picking tools, bump keys (where appropriate) and bypass techniques to manipulate the cylinder pins without forcing the lock. Your existing cylinder usually keeps working perfectly afterwards.
When damage may be unavoidable
Some situations make damage-free opening impossible — for example a deliberately broken-off key blocking the cylinder, an internal mechanism failure, or a high-security multi-point lock that has fully engaged. In those cases the locksmith should explain the options and the price before drilling.