Here’s a tip. If you’re having trouble getting the Ruler menu item to work, i.e. be activated rather than grayed out, be sure to click into the $Text area before you navigate up to Edit>Text>Show Ruler or use the short cut ^⌘R (cntrl+cmd+r). Tinderbox can’t read your mind. It takes contextual cues from your behavior, e.g. click in the $Text pane. The Rule is only relevant when the $Text area is active, so there is no reason to have it available in any other context. NOTE: once you enable it, it will be there each time to you return to the $Text area.
Acknowledgment: Tip encourages thanks to questioning in YouTube comment- Jean-Pierre Marceau - YouTube.