// Connects the joint to the world instead of another rigidbody
hingeJoint.connectedBody = null;

// Connects the joint to another body
var otherBody : Rigidbody;
hingeJoint.connectedBody = otherBody;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Rigidbody otherBody;
    void Example() {
        hingeJoint.connectedBody = null;
        hingeJoint.connectedBody = otherBody;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public otherBody as Rigidbody

    def Example():
        hingeJoint.connectedBody = null
        hingeJoint.connectedBody = otherBody