Reference tags in each of the components of the interchange assembly identify placement references in the target assembly. The reference paring table is an efficient way to pair reference tags from the active component (the one that will be replaced in the target assembly) to reference tags of one or more components in the interchange assembly. Required references (indicated by ) must be paired, while optional references can be left unpaired. The reference tags from the pairing table are used to replace the active component in the target assembly. The reference tags created are visible in the Model Tree Footer folder.