I think a curvy log cabin block is one where the logs are 2 different widths. So for instance, the dark side is all 2" wide and the light side is 1".
1) Since there are several brands of rulers out there, can you give us the manufacturer, that way someone can give you specifics.
2) I would google curvy log cabin
blocks. There are lots of you tube videos out there and knowing how to construct the block might give you clues on how to use your tool.
Here's one:
https://www.youtube.com/watch?v=82wUlDzU8aI