Sometimes I find myself at a page containing the last part of an office before the final blessing. Rather than having to flip back to a page containing the final blessing, this divider keeps it handy and is the last divider in the group of red-bordered dividers kept in a group and moved day by day in the Ordinary/Weekly Psalter pages 935 - 1141.
For example, if its Vigils for Saturday, I would have the following dividers all at page 1124:
Lauds Psalm 67
Benedictus for Lauds
Magnificat for Vespers
Final Blessing
The next group of dividers are for the special feast/memorial days in the
back sections BDP. They are all on black-bordered tabbies.