Centroid velocity residuals traced by ¹²CO emission for all discs, referred to each disc reference frame. The annotated solid lines mark the radial location of millimetre dust rings (denoted as Bxxx), and the purple dotted line that of the most prominent kink identified by eye in ¹²CO intensity channels (denoted as Kxxx). Also shown is the north-sky (or PA = 0°) axis for reference. The oblique shape of this axis is due to the deprojected geometry of each disc vertical structure retrieved by the best-fit models. The circle in the bottom left corner of each panel indicates the location of the blue- and redshifted side for each disc. These maps illustrate the deviations from Keplerian rotation of the gas component located at high elevations (0.2 < z/r < 0.4) over the midplane.