Multiframe adopts the convention that joint 1 is always the joint to the left of the member in the front view and in the case of members which are vertical joint 1 is at the bottom, joint 2 at the top.
 
In the case of a member which lies in the xy plane, joint 1 will be the joint on the left and joint 2 will be the joint on the right. In the case of a member which lies in the xz plane, joint 1 will be the joint on the left as viewed in the right hand view and joint 2 will be the joint on the right as viewed in the right hand view.