What do synchronized functions mean exactly?

I was trying to write thread-safe code on Java 1.4 with its pre-JSR 133 broken memory model and everything, and I thought synchronized function just synchronized that function, but it doesn't! Synchronized function synchronizes across all synchronized functions of the same instance.

synchronized void function()
{
   int two = 1+1;
}

is really just short for

void function()
{
   synchronized(this)
   {
      int two = 1+1:
   }
}

same thing with synchronized static functions, except they synchronize on Foo.class