Source: Standard literature
Ādāra-koṇḍu or "plain lines" is the Sinhalese term for a decorative motif that consists of lines.1
Ādāra-koṇḍu lacquer work decoration on the shaft of a Sinhalese patisthānaya.
They are the plain lines perpendicular to the shaft's length that divide the other motifs.
Sold by Mandarin Mansion in 2019.
Article: Sinhalese lacquer work
1. See Ananda K. Coomaraswamy; Medieaval Sinhalese Art, Pantheon Books, New York, Second Edition of the 1908 original, 1956. Page 216-217.