Principal elements of the fan-spine structure involved in the flare SOL2005-05-06 schematically sketched over the SDO/AIA image in the 304 Å band at 02:16:20 UT. The chromospheric kernels are outlined by the yellow ovals: R1+R2 is the circular ribbon structure, where the inner ribbon R1 and the circular ribbon R2 are shown in detail separately at 01:55:49 UT within the dotted rectangle; R3 is the remote ribbon; R4 is the elongated ribbon seen at the decay phase. The fan-spine magnetic structure is drawn in green and magenta: the fan lines (magenta) form the inner spine; the dome lines (green) continue into the outer spine (a long loop anchored at R3 kernel); a quasi-separatrix layer is the surface between magenta and green lines (is not shown here) with the magnetic null-point located between the inner and outer spines (Pariat et al. 2009). Loops in blue connect the sunspot (dark pink) with R3 and R4 kernels.