To hallow is to make sacred, or to make holy.
Just as we have two words in English, so there are two ancient Germanic words: Proto-Germanic *hailagaz is the ancestor of Anglo-Saxon hálig, Old Norse heilagr, “holy,” and “hallow,” and Proto-Germanic *wíhaz is the ancestor of Old Norse vé and Anglo-Saxon wíh, wéoh. It is not certain whether a firm distinction of meaning was ever made, or whether the two tended to overlap in meaning, as “sacred” and “holy” do except for some theologians. By convention, heathens usually use vé for a sacred place or dedicating an altar, and “hallow” for dedicating offerings.
There are two ways of making something sacred, which can be used separately or together. Both involve calling on Thor/Thunor as protector of Miðgarð/Middangeard and of humankind. One is hallowing with fire; this is based on the land-taking ritual that the Icelandic settlers used when starting a new settlement, and on a detail in saga descriptions of veizla. The other is the hammer rite; this was invented by Edred Thorsson based on the use of the Mjöllnir symbol to protect heathen runestones and as an amulet, on a mention in one of those sagas that the goði “signed” the food and drink, and on the interpretation a courtier gave when a Christian king, Hákon the Good, made a sign over his food.
To make a vé, i.e., to prepare a blót place, using fire: Stand at the north edge of the space to be defined, facing north and up. Strike fire (some heathens use needfire for this purpose) and call on Thor/Thunor to protect the place. “Thor, hallow this holy place” is a conventional formula; it is traditional to raise both arms, like the rune elhaz, or one can raise only the hand bearing the fire. Keeping the flame lit, carry it clockwise around the boundaries of the space (if using a needfire, the best procedure may be to light a candle or lamp from the needfire and carry that). At each corner, or at the other compass points in the case of a circular space, stop, raise the flame, and repeat the request. If the fire goes out, stop, rekindle it or relight it from the needfire, and repeat the formula before proceeding. Repeat one more time at the starting point.
To make a vé using the hammer rite: Stand either in the center of the space to be defined or on the north side of it within its boundaries. Face north holding up a hammer (a small sledgehammer is commonly used; the hammer around one’s neck may also be used), the horn that will be used in blót, or some other symbol of the gods (such as a spear or drawn sword); or one can simply point one’s finger. Trace the sign of a downward-facing hammer in the air (down, left, across to the right) while asking Thor to hallow and protect the place, and visualizing Mjöllnir itself. Turn to face east and repeat. Turn to face south and repeat. Turn to face west and repeat. Then return to facing north and repeat looking upward. Then repeat looking down. There are many variations on the hammer rite, including different spoken and sung formulæ, some in one of the Old Tongues, some including the runes and the four intermediate compass points, some invoking the landwights for protection also, some omitting the upward and downward directions, some relating each direction to one of the nine worlds (beginning with Asgard in the north) and involving color-visualization and different pitches of the voice for each. But the basic formula given by Edred Thorsson in A Book of Troth (p. 139) was “Hammer in the north! Hold and hallow this holy stead!” and so on for each compass point, then “Hammer above/below me/us! Hold and hallow this holy stead!” At a group blót, the other participants stand and turn to face in the same directions with the hammer-signer; in some groups they speak in unison.
It is possible to combine both, and to make the creation of the vé processional; an example of this is the Wéonede Song used by the former Angelseaxisce Ealdriht.
Making a vé can be thought of in two ways, or varying combinations of them: making a hospitable place before inviting the gods to share one’s offerings, and making a safe place. In either case, most heathens see no reason to undo the vé once it is made, unless blóting in an area also used for other purposes, such as a living room or a shared worship space. There are thus no equally widespread traditional ways of unmaking the vé at the end of the blót, but one method is to thank the wights and tell them they are free to go about their business again. Unmaking the vé is not a duty, not a normal part of the blót ritual; normally it remains sacred space.
Traditionally, an outdoor vé was surrounded by an enclosure, so if you set one up in your yard you may consider fencing it off.
Usually if a new altar (stalli, hearg, harrow) is to be dedicated within a new vé, the vé is created first.
To dedicate an altar using fire: Stand with the altar in front of you, facing north. Kindle fire and raise it; standing looking north and upwards, ask Thor/Thunor to hallow the altar. Pass the flame across the surface of the altar, mentally dedicating it to sacred purposes. Optionally, splash a little of the drink to be sacrificed on the surface and smooth it over it with your hand.
To dedicate an altar using the hammer sign: As above, making the sign of the hammer in the air and over the altar. It is possible to combine the two methods by making the hammer-sign in the air and over the altar using the flame.
Opinions vary among heathens regarding whether edged weapons (or firearms, where legal) should be permitted within a vé. One school of thought is that a vé is a frithstead, and the heavily armed Icelanders bestrode a frithstead only with their swords immobilized by “frithbonds” that prevented them from drawing them, and so we should check our weapons at the door when we blót. The other school of thought is based on statements by Roman observers that among the ancient Teutons, a man (and one presumes a woman) never went unarmed after infancy, and that in their assemblies they signified assent by raising and clashing their swords. So some heathens expect everyone to be armed at all times (as per Hávamál 38). As stated above, adherents of this school of thought may use naked blades to actually hallow the space. When attending a group blót, therefore, it is advisable to ask about the policy, or observe which custom is being kept. The traitorous Northumbrian high-priest, Coifi, desecrated the temple of Freyr/Frea by throwing a spear into it; so some heathens believe that at a blót specifically to the Vanir one should not carry weapons, or some say wear any metal whatsoever, including hammers, watches, and bra buckles.
In other ways, the respect to be shown within a vé is similar to that in other religions. One should be clean and wearing clean clothes; some like to show added respect by going barefoot and with unbound hair. One should avoid unnecessary and thoughtless speech, listen carefully to others’ hails to the gods, and echo them with a simple “Hail … !” Unpleasant bodily noises are to be avoided if possible, and while one may leave and return during the blót, it should be avoided and if possible a break should be made between rounds to accommodate it. Laughter is ok; mockery is not. The gods are present, and the wights are also listening in. Most heathens believe one should stand throughout a blót unless it would be a great hardship; some, particularly Anglo-Saxon heathens, may kneel, put their hands together in prayer, or even prostrate themselves in solo blót, but many in the Ásatrú tradition believe these are inappropriate for free adherents of a religion whose gods do not treat us as slaves.
To hallow the offerings at a blót, one may simply raise them in turn to the north after the vé is created and then leave them there, on the altar if there is one; or make the sign of the hammer over them (hammersign them), which some also make a practice of doing over their food before every meal; if using this method, the horn should be hammersigned after every refill. Or if using fire, pass each offering over the fire (a candle or other flame is usually left burning on the altar for this purpose), saying “Thor, hallow this drink/food/gift.” If using fire at a large drinking blót, one usually hallows all the bottles before charging the horn(s). Hallowed food and drink that are not consumed should be disposed of on earth or grass or in the fire within the vé, not taken away and otherwise used. They are sometimes given specifically to the wights.