Click the Home tab→Select group→Activate Part 
button.
Click the part(s) that you want to activate in a draft quality view.
The part is available for dimensioning and other operations that require precision.
Tip:
The view must be up-to-date to activate a part in it.
You can activate parts during view creation by checking the Create Draft Quality Drawing Views box, then the Activate Parts for Dimensioning box, on the Drawing View Options tab of the Drawing View Wizard.
When you convert a draft quality view with activated parts into a 2D view, the elements of the activated parts are placed on a hidden layer.