#### Second Extension

The Second Extension drop-down list becomes available only if the item chosen in the Extension drop-down list requires the addition of a second extension in order to form a useable expression element.

Example: Suppose you are referencing the nominal value of the X location axis of a dimension named "D1".
You would:
Choose D1 from the ID drop-down list.
Select X from the Extension drop-down list
Select Nom from the Second Extension drop-down list.