I scan many slides, transparencies, and negatives. I need to straighten them often. I would like the ruler/measurement tool under CTRL-I to remain as the default with eveery start of Photoshop. Is it possible to make it the default instead of the eyedropper tool? Perhaps a shortcut key of its own might work as well... where one keystroke will bring it to the top... will it stay there? hmmm. . . I've just given myself an idea... (LOL)
You can assign shortcuts and have the ruler set to pop-up when you hit a key. Go Edit > Keyboard Shortcuts > Select
PS should remember your tool you used last in the set and keep that at top, make sure you close properly for PS to "remember"