Lock Field in Family Types Dialog

[Batman]

When creating families there is a field in the Family Types dialog titled 'Lock'

Can someone please explain to me the use of this field?

[Batman]

Or please point me to a resource that can explain it. I am having trouble finding it in the help.

[richardblack]

Here is a screencast that does a good job at explaining:

http://www.screencast.com/t/tg0TKdUGg

[Alex Page]

...and has no affect on the family when loaded into the project