This is the only sensible way to oil control cables. The tool's rubber boot with the small end grips the inner wire of the cable whilst the outter is gripped by the other end. The screw is tightened up which ensures a seal around both ends. The straw of your lightweight oil aerosol (WD40 or equivilent) is pushed into the small hole in the bottom of the tool. When the button on the aerosol is pressed oil is forced into the void between the inner and outer parts of the cable. Keep going until oil is seen dribbling out the other end. Remove the tool and pull the inner cable in and out a bit. Job Done!<<