Repeat behind?

For some years I’ve been using a symbol for “repeat behind” which has been pointed out to me is non-standard! It’s a fold behind arrow with a dash through it (and optionally, as shown right) which steps to repeat).

I’m not sure where my use of this symbol it came from, but I’d be very interested to know how other diagrammers tackle this thorny issue?

I’m also torn on the fold/unfold. For years I used a line going to the location then returning. more recently, I’ve adopted the single line with solid/hollow arrowheads.

fold unfoldThis then leaves the issue of where you fold/unfold and it doesn’t matter which way, such as an initial diagonal. Here, both arrowheads are conventionally solid. Is this wasting a symbol and possibly adding an extra level of confusion? Should I always use “one end hollow”?

I’m losing sleep on this – your thoughts welcomed!

repeat behind