On Thu, 24 Apr 2014 13:04:33 +0100, The Natural Philosopher wrote:

How can you expect dog clutches to synch and mate if both halves are
static.

Both halves aren't static - there's always a bit of drag on the clutch,
so the input shaft'll be lazily spinning, with no real torque on it.

But even if you switch the engine off, select first, then try to push the
car, you should find it's gone in gear.