I was thinking a slip knot for the neck, then tie the two loose ends using a constrictor knot, one for each loose end, around the beam. That is if you're planning on doing a full suspension hanging. Be warned though, the constrictor knot is so effective it can even damage the beam if it's not of a hard enough material. From my knots app: "Simple and secure, it is a harsh knot that can be difficult or impossible to untie once tightened."