Also called Hamarsmark, this ritual is found mentioned specifically in Hákonar Saga Góða ch. 17:

En er hit fyrsta full var skenkt, þá mælti Sigurðr jarl fyrir ok signaði Óðni ok drakk af horninu til konungs. Konungr tók við ok gerði krossmark yfir. Þá mælti Kárr af Grýtingi; hví ferr konungr nú Svá? vill hann eigi enn blóta? Sigurðr jarl svarar: konungr gerir svá, sem þeir allir, er trúa á mátt sinn ok megin, ok signa full sitt Þór; hann gerði hamarsmark yfir, áðr hann drakk.

And when the first full was served, Jarl Sigurðr announced it and signed (signa) it to Óðinn and drank from the horn to the king. The king took it and made the sign of the Cross over it. Then Kárr of Grýtingr spoke: ‘Why does the king do that now? Does he not want to worship?’Jarl Sigurðr replied: ‘The king is doing what all those do who trust in their might and main and dedicate their toast to Þórr. He made the sign of the hammer over it before he drank.’

This idea of signing over the full (round of the Sumbl) is significant and is mentioned in many sources. Again, in Hákonar Saga Góða ch. 14 we see “then shall he sign the full and all Blót-meat” (þá skyldi hann signa fullit ok allan Blótmatinn). In Sigrdrifumál 7-8 we are told to “sign the full” (full skal signa) and protect the mead with leeks. In Ólafs Saga Helga ch. 94 we are told that they signed the minni. So, in each case the Signing or Signa is seen to bless a full or round of the Sumbl. Of course, we know that the hammer is used for much more than that (See Hamarr), but this does give us a significant amount of source material to build upon the performance of a signing with it. The fact that it is said in Hákonar Saga Góða to look exactly like the Sign of the Cross, gives us some method of establishing how it could be performed. Since the primary role of Þórr is as the protector of his family, the Æsir, it seems only appropriate that the Hammersign be performed using his immediate family as the basis.

In Egils Saga ch. 44 we find a parallel to the above mentioned Sigrdrifumál passage. We shall look at both of these to make a clear comparison between the two. These tell us that the mead can be blessed and purified with rúnar. First, Sigrdrifumál 7-8:

Ölrúnar skaltu kunna,

ef þú vill annars kvæn

véli-t þik í tryggð, ef þú trúir; á horni skal þær rísta

ok á handar baki

ok merkja á nagli Nauð.

Full skal signa

ok við fári sjá

ok verpa lauki í lög; þá ek þat veit,

at þér verðr aldri meinblandinn mjöðr.

Now we look at Egils Saga ch. 44:

Ölrúnar shall you know,

if you will not have

another’s wife betray your trust; on the horn shall you rist

and on the back of the hand

and mark Nauð on the nails.

The Full shall you sign,

and guard against peril,

and a leek cast in the liquor: then I know that you

will never have mead mixed with treachery.

Þá gekk Bárður til drottningar og sagði henni, að þar var maður sá, er skömm færði að þeim og aldregi drakk svo, að eigi segði hann sig þyrsta. Drottning og Bárður blönduðu þá drykkinn ólyfjani og báru þá inn; signdi Bárður fullið, fékk síðan ölseljunni; færði hún Agli og bað hann drekka. Egill brá þá knífi sínum og stakk í lófa sér; hann tók við horninu og reist á rúnar og reið á blóðinu. Hann kvað:

Hornið sprakk í sundur, en drykkurinn fór niður í hálm. Þá tók að líða að Ölvi; stóð þá Egill upp og leiddi Ölvi utar til dyranna og hélt á sverði sínu. En er þeir koma að dyrunum, þá kom Bárður eftir þeim og bað Ölvi drekka brautfararminni sitt.

Bárǫðr bade him drink and stop that jeering. Egill drained every cup that came to him, drinking for Aulvir likewise. Then Bárǫðr went to the queen and told her there was a man there who put shame on them, for, howsoever much he drank, he still said he was thirsty. The queen and Bárǫðr then mixed the drink with poison, and bare it in. Bárǫðr signed the cup, then gave it to the ale-maid. She carried it to Egill, and bade him drink. Egill then drew his knife and pricked the palm of his hand. He took the horn, scratched runes thereon, and smeared blood in them. He sang:

Rístum rún á horni, rjóðum spjǫll í dreyra, þau velk orð til eyrna óðs dýrs viðar róta; drekkum veig sem viljum vel glýjaðra þýja,

vitum, hvé oss of eiri ǫl, þats Bárǫðr signdi.

Rist we runes on the horn,

redden all the spell with blood;

wise words I choose for the cup wrought from branching horn of beast; drink we then, as drink we will, draught that cheerful bearer brings, learn that health abides in ale,

holy ale that Bárǫðr signed.

The horn burst asunder in the midst, and the drink was spilt on the straw below. Then Aulvir began to be faint. So Egill stood up, took Aulvir by the hand, and led him to the door. Egill shifted his cloak to his left side, and under the mantle held his sword. But when they came to the door, then came Bárðr after them with a full horn, and bade them drink a farewell cup.

This ritual is the cornerstone for many of the ceremonies found within this book, for it is used to consecrate various things from sacred items to holy spaces. The ceremony can be performed using one’s fist or a ceremonial Þórr’s Hammer, or Mjǫlnir. The Sedian path decided to develop a rite that is built upon the family of Þórr, beginning with his Father and ending with himself. Óðinn is the God of the mind and thus we touch the forehead to honor him, Frigg is the Mother and Goddess of Love, so we touch the heart to honor her. Baldr is the God of peace and thus Þórr's counterpart, so we touch the left shoulder in his name. Finally, we touch the right shoulder in respect to Þórr himself, ending the process with the mighty hallower. This is based upon a popular rendition of the rite in modern Heathenry, and can certainly be used.

We can also consider the above Hákonar Saga Góða passage that states a Sign of Óðinn existed on its own, which may lead us to believe that the sign was simply about Þórr and Þórr alone. If such were the case we could consider different names of Þórr as the “stations” of the rite, which would certainly fit with the overwhelming polyonomy we find within our lore. Þórr is also called Atli, Ásabragr, Ennilangr, `Eindriði, Björn, Hlórriði and Harðvéurr, Véurr, Vingþórr, Sónnungr, Véuðr, and Rymr. As we saw under the description of the Hamarr, the rite concludes with the formula found on runestones, Þórr Vigi, or “Þórr Consecrate.” There is no doubt, as we view the extant sources, that the hammer is used as a tool of consecration, and the Hamarsigna rite is the best mode we have towards that end.

-Excerpt from Æfinrúnar, book 1

https://norroena.org/product/aefinrunar-a-sedian-book-of-rites-and-prayers/