Persistant guidlines.

 From:  Michael Gibson
77.2 In reply to 77.1 
I want to add this at some point, but then there will need to be provisions to select and delete them later on... It will be a little fussy because you probably don't want to select them all the time like regular geometry because they'd get in the way.

It's those additional tasks that make keeping them somewhat more work than it first appears.

- Michael