A cable lockout assembly to tightly secure a cable that is arranged in a looped configuration with valves or switches in an ON/OFF or partial ON condition. A base includes a through passage for the cable. A rotatable piece is mated relative to the base for rotation about a central axis screw. The rotatable piece can be confined to the base by a conical washer on the central axis screw. A tool for rotating the rotatable piece engages with clamping force with the rotatable piece to fasten or unfasten the cable inserted in the through passage by fastening the rotatable piece over the base when the cable is placed in between the rotatable piece and the base. A cable manner is also employed to hold the wound cable and prevent loss of cable when the lockout is not in use.