From Sewing Patterns by Mrs H:
The Convertible Bag was designed for the Bag of the Month Club 2014. The pattern makes an excellent everyday bag that quickly converts from cross body to a backpack.
Summary
Bag of the Month Club 2014 pattern
Easily convert the bag from a cross body bag to a backpack using the adjustable long strap
Dimensions
Finished dimensions of 9" x 11" x 2" (23cm x 28cm x 5cm)
Bag Features
The compact bag size is perfect for errands or a day trip where you don't want to haul around a giant bag. The long strap converts this bag from a cross body bag to a backpack with a couple of easy steps. You simply unclip the strap, thread it through the back 'tunnel' and re-clip it to the bottom D-rings. The bag also has exposed boxed corners and a zippered corner on the back.