See also: Delete Dependent Elements
Many elements reference (need) other elements.
The Elements References dialog-box (Read-Only) is the list of elements (called the Reference Elements) that must be in the model to build a more complex element.
The list includes each Reference Element name, its Reference Element Type, and its Reference Element Owner.
When you add a Pin-Joint, you select two Points in two different Parts.
Thus, the Pin-Joint must reference (needs) the two Point elements.
To see the Reference-Elements of an element: