Usually the insulation is placed between the rafters and nailed or stapled to the rafters with flanges to be airtight. The bars are in the same locations where the staples are visible.
In the pictures below, you can clearly see where the rafters are at the bottom. Above these rafters you can also see where the insulation is attached and you will also be able to feel the rafters.
To attach a Penta Power Home Tag, you can glue it to a Penta Power plexi for Home Tag and then attach it diagonally with 2 screws at the desired location on the rafters.
Check out the images below for more clarity:
