The SLX4 protein functions as a platform for catalytic subunits of structure-specific endonucleases. Findings reported in Cell (Fekairi et al., 2009; Svendsen et al., 2009) and in Molecular Cell (Andersen et al., 2009; Muñoz et al., 2009) now identify the human SLX4 and show that in association with the SLX1 endonuclease it directs the symmetric cleavage and resolution of Holliday junctions.