In the grease pencil menu there is an option for adding rulers and protractors.
Now, as far I understand, I can remove all rulers by pressing ESC but if I press ENTER instead rulers get saved.
In various places (prominently, in a kind of help line while in ruler/protractor mode) it is said that pressing DEL will delete rulers, but I cannot get it to work. (tried in Blender 2.71). Is it a bug, an error in the docs, or am I misunderstanding the context of this operation (e.g., how would I select a ruler so that I can delete it?)