Edge-on views of the best-fit outflow model for (a) Mrk 509 and (b) PDS 456. For clarity, the PA for both configurations is adjusted to 180°, and the BLR centre is positioned to the origin. The LOS at the best-fit inclination angle is shown as a black arrow. The midplane, represented as a green line, is defined as the line passing through the origin and is perpendicular to the LOS at i = 0°. The regions above (closer to the observer) and below (farther to the observer) the midplane are also labelled. The colours of each cloud refer to their LOS velocity, while their sizes reflect the weight given to each cloud towards the total emission; the larger the size of the cloud, the more this cloud contributes to the broad-line emission. The edge-on view of the BLRs of Mrk 509 shows that its asymmetry is due to a highly obscuring midplane; for PDS 456, a preference for broad-line emission to come from the far side of the BLR.