The [docs for parking\_lot](https://github.com/Amanieu/parking_lot) say:

> 
> 12. `Mutex` and `RwLock` allow raw unlocking without a RAII guard object.
> 13. `Mutex<()>` and `RwLock<()>` allow raw locking without a RAII guard object.
> 
> 
> 

There is no further mention of these features, what they mean and how to use them. What are some pointers or sample uses?