Making the sign of the Hammer, particularly as a blessing over the mead horn in our sacred rites has well defined roots in Germanic history. In Snorri Sturlason's Saga of Hakon the Good in Heimskringla King Hakon of Norway is required as leader of his people to participate in the festival of sacrifice at harvest. He is reluctant to do so as he is a xtian but understands that ultimately he has no choice if he wishes to retain his crown.
"The king accordingly sat upon his high-seat. Now when the first full goblet was filled, Earl Sigurd spoke some words over it, blessed it in Odin's name, and drank to the king out of the horn; and the king then took it, and made the sign of the cross over it. Then said Kar of Gryting, 'What does the king mean by doing so? Will he not sacrifice?' Earl Sigurd replies, 'The king is doing what all of you do, who trust to your power and strength. He is blessing the full goblet in the name of Thor, by making the sign of his hammer over it before he drinks it." (Chapter 18)
When we make the sign of Thunor's Hammer we perform an act of sacrifice for we are blessing the mead or whatever the substance may be in His name and sanctifying it. The Hammer was not only a weapon of war against the etins, the agents of chaos but the bringer of rain and fruitfulness. It played a prominent part in wedding ceremonies and in leagal matters, surving today as the judge's gavel. Also of course we have the myth of Thor blessing Bardr's funeral pyre.
The reader will note that whilst we make the sign of the Hammer over the horn we actually say a blessing in the name of Odin/Woden/Wodan/Wotan. We invoke the energies of both Gods in this act.
Full details on making the sign of the Hammer may be found in my article The Sign of the Hammer posted on my Die Armanenschaft der Ario-Germanen blog on 21/11/10.