Typical fits of synthetic spectra (red solid lines) to the observed Zn I line profiles (marked by vertical ticks) in the 2dF/HERMES spectra (filled gray circles) of the target RGB stars S1800 (top row; T_eff = 4510 K, log g = 1.90) and S167 (bottom row; T_eff = 4390 K, log g = 1.60). We also indicate zinc abundances A(Zn) determined from each spectral line, together with their errors (Sect. 2.2). The quality class of the Zn I line is indicated at the top of each panel (see Sect. 2.2 for the line class definition).