Estimated radii from the BH where different observed optical emission lines are produced in AT 2019avd, compared with various key physical length scales predicted in the literature (assuming log [M_BH∕M_⊙] = 6.3). The pericentre and circularisation radii are computed assuming a Sun-like star incident on this BH with its closest approach at the tidal radius. Similarly to Kollatschny et al. (2014), we see evidence for a stratified BLR. The coloured lines represent length scales that were obtained based on observations of AT 2019avd, whilst the grey dashed lines are based on various scaling relations in the literature (BLR radius based on Kaspi et al. 2005, whilst the inner torus radius was computed using Eq. (1) of Nenkova et al. 2008, assuming a dust sublimation temperature of 1500 K).