Another good example of the tar paper being layered over the sheet below it can be seen here. You should be able to see what is meant here in the lower right corner, how the sheet above overlays the sheet below.
You can also see the tar paper barrier being fitted to the recessed shampoo boxes. Though the fitting is rough, it will be much more thorough by the time the tar papering is done and we are ready for the next step. Until then though, this will do fine.