Teĥum Shabbat is specific to every individual, based on his location. For example, let us say that the homes of two neighbors (who do not live in a city) are located 1,000 amot apart from each other. Each neighbor has his own teĥum Shabbat, part of which overlaps with his neighbor’s teĥum Shabbat, and part of which does not.
The laws of teĥumin apply to one’s animals and belongings, and to Jews as well as non-Jews (see n, 12 below). Therefore, if one carried his talit to the edge of his teĥum, and his friend wants to borrow it but has a different teĥum, the friend may not carry the talit beyond its owner’s teĥum (SA 397:3). If the talit is jointly owned, it may be carried only where their teĥumin overlap (ibid., 397:9).