Locking on field or local variable?

Question

After I read this question with an answer from Marc....

I sometimes see people locking on a local variable.

Is this code broken?

Answer 1

I, personally, don't see any reason of using this, as lock just sets the special field in the instance of the o, to signaled state. So other threads can check the state of that instance, and based on that execute the code inside the lock statement or wait release of it.

Having local variable every time will allocate a new instance, so for every thread it will be ok.

Don't see any meaning in this.