Not sure, Northdad. Maybe perimeter based or even map scales for the conversion type questions. Questions where measuring the line is the first step of a multi-step problem.
I wish her all the best for her test. Have they asked for rulers in tests in the past? Sorry, I am not familiar with the HBS test.
Thanks for the suggestions enjoythejourney and Ladymuck. I've no idea whether this is the first time they've asked to bring rulers as there are no past papers.
Does anyone else know?