How to let a camera stay active in scene way although selecting another element

Hey,

i temporarily go through a tutorial , and make a 2d game. OS there i can add sprites to my 3d application over a second camera. If i select the camera , i can see the boundaries of the camera view and could position all the elements properly, but if i select another element, this boundaries vanishes. So my question, is there an option to see these boundaries all the time long, whatever you select?
THX