One-dimensional visualisation of the group finder algorithm TD-ENCLOSER introduced in this section. The points in the three panels are identical and each point represents a galaxy. Galaxies belonging to the same group as coloured accordingly. The contour levels from bottom up are ρ_outer (solid), ρ_saddle (dashed) and ρ_peak (dotted). The outcome of the first pass is shown in the first panel, where galaxies are assigned to groups based only on the contour morphology, shown as the grey curve. In the second pass, outliers are disconnected from their groups based on the density of their N_merge − 1 neighbours and are tagged as isolated. In the third pass, each ejected galaxy is assigned to a new group. All galaxies which were not clipped in the second pass are shown as faint to indicate that they are considered to be absent in the third pass.