I made this a while ago for supporting Year 7 students on directed number (i.e. positive and negative numbers). I think there is something more intuitive about a vertical number line – if you are adding you go up, subtracting you go down. Having said this, I have always had a horizontal number line across the top of my board!
If the number line is stuck on the inside back cover of the exercise book, it is always there whatever page the child is working on. It can then be folded safely away whether using large or small format books.
Doing some work in primary this week, I realised that the same idea could be useful for supporting younger children learning the essential skills of counting back and counting on when doing addition and subtraction of positive numbers. So I have made another version just with positive numbers.
The end points of these lines are arbitrary of course. I have deliberately gone for something a bit random to start a discussion, “Sir, why does it stop at 44?”. But if that offends your preference for order in life, then feel free to adjust it on the spreadsheet that I used to create the pdfs in the first place.