Are you sure the slots were there to draw lines? Did it square up any block or just a specific one, like a HST? I'm wondering if it was the discussion on Bloc Loc HST rulers. There are no slots, but there is a groove that sits over the seam and allows you to trim perfect HSTs. They are pricey.
Other than that, June Taylor has quite a few different rulers with cutting slots.
Last edited by PaperPrincess; 12-19-2015 at 08:00 PM.