Forwards, I'm the hidden bit at bottom of a blade Backwards, I'm a tiny flying pest you swat away

A cutting tool or fast boat.

One may be served with butter and jam, another with champagne in a lifted hand. One helps begin the morning right, the other honors a person on a special night.

In yawning mouth that never bites are many pointed fangs Irregular in placement, some below, but me? I hang. I dribble spittle from above, like ravenous carnivore A rumbling from deep below may crash me to the floor

Stands out on the farm, Keeping horses and friends Safe from winter and harm.