Dept. of Subtle - Family Editor Parameter Lock

A recent exchange at the RevitForum.org reminded me of this subtlety. The Family Types dialog introduced the concept of locking a parameter.

You can select a reference plane and the dimension changes to blue like "normal" when the parameter is un-locked. When it is locked you can edit the dimension value by selecting the dimension, which is counter-intuitive because that's how we create a dimension override in the project environment. I believe the lock check box is "supposed" to lock out editing in canvas but they left a "back door" unlocked (pun intended).

It is easiest to see this in action so I did a quick video demo.