Plane-of-sky magnetic-field strengths in the 1°-wide squares chosen along the Reticulum (magenta) and Eridu (green) filaments, in the fibre (top) and shell (bottom) geometries, using the S_v dispersion function in the ST (dark filled symbols) or DCF method (light open symbols). The data points and error bars respectively give the mean value in each ~5 pc-wide square and the rms dispersion at 0.5–0.7 pc scale inside each square. The offset distance of the DCF data points has been slightly enlarged for clarity. The grey band shows the mean CNM B_sky value from Heiles & Troland (2005) assuming $B_{\text{sky}}^2=\frac{2}{3}{B}^2$.