In English, a taglock is a matted bunch of wool or hair. Metaphysically speaking, a taglock is a personal item that creates a link to the target.
Taglock in Magick
If the taglock is from a person or animal, you might use hair, bodily fluids, a photograph, personal clothing, something bearing their signature, or fingerprints (or a paw print); any other item that can create a sympathetic link with the target of a spell.
If your target is a location rather than an individual, a suitable taglock might be a key to the building, some dust from a shelf inside the building, stone from a pathway, a bit of chipped paint, etc. Or, of course, a photograph. For a business, you might use a business card or some of their stationery with their letterhead on it.
The use of the taglock in the spell can vary. It can be used alone, placed inside a witches bottle or added to a poppet or other representational item.