Insert the thin end of the wedge.
Thereal reason that Japan is so hell-bent on continuing its whaling isbecause it fears that a ban would be the thin end of the wedge.
The government says it only wants to privatize one or two railway lines, but I think it's the thin end of the wedge . They'll all be privatised soon.
I do not mind if you stay out late for once, but you must understand that it's not the thin end of the wedge and won't become a regular thing.
The principle of unity has been discarded and the thin end of the wedge of disruption driven in.
If the cost of steel rises it is usually the thin end of the wedge.