It's difficult to write a meaningful review of a small plastic box but let me reassure you, they do exactly as it says on the lid. Yes, they lock and lock. And they lock very securely and they certainly help keep food fresh. I'm particularly impressed at how well they keep cheese from going mouldy.
Beware , however, of the new non-staining version which I bought from another supplier. They're exactly the same shapes and sizes and they function the same way but they're harder and they're annoyingly fragile. Also, the lids don't seem to fit so well so keep to the regular model.