Some rulers, triangles come to mind, have one or more tips cut off. The same ruler from a different brand may be pointy. If you are cutting from strip sets, the strips would need to be cut at different widths, or you need to know how to position rulers from different brands.
The reason why the points are cut on some is to allow you to cut squares and triangles from the same strip and/or to make piecing easier to match seams.