Lat. In old practice. A file; 4. e., a thread or wire on which papers were strung, that being the ancient method of filing. Filum aquae. A thread of water; a line of water; the middle line of a stream/of water, supposed to divide it into two equal parts, and constituting in many cases the boundary between the riparian proprietors on each side. Ingraham v. Wilkinson, 4 Pick. (Mass.) 273, 16 Am. Dec. 342. Filum forestse. The border of the forest. 2 Bl. Comm. 419; 4 Inst. 303. Filum vise. The thread or middle line of a road. An imaginary line drawn through the middle of a road, and constituting the boundary between the owners of the land on each side. 2 Smith, Lead. Cas. (Am. Ed.) 98, note.