Difference between lock(this) and a lock on static object

Question

Which of the following two code snippets is better to use?

static readonly object _locker = new object();
lock (_locker)

or

Answer 1

Because you don't want the lock to be accessed from outside the object.

If you use lock(this) you can get a deadlock:

void blah() {
   lock(this);
   sleep(200);
}

//Some other block of code

MyObject a;
foreach(Mythread m in threads)
{
   lock(a);
   m.Call(a.blah); //Not the best syntax, but you get the idea.
}

If you keep the lock inside the object it wouldn't deadlock.