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Before the sex has begun, the female lays down and spreads her legs wide open. The male then steps back about 15-20 ft and gets a running start before penetration. If desired target is missed, you're not norwegian.

This manuever is typically performed before or after the Canadian Goose.
"The Norwegian Hammer is quite the rush!"

"Jill was never the same after her un-norwegian boyfriend attempted the N-Hammer."

"Your mother enjoys the Norwegian Hammer"
by Paul Bunyon July 27, 2006