Because this roof is a lower slope than four in 12 they must overlap the courses significantly normal overlap of four inches.
Roof dry in.
Roof dry in flashing and underlayment.
Building dry box or dry in should include at least the following the structure is complete or if necessary temporary structural supports may be in place sufficient to permit interior.
For slopes lower than 4 the overlap is 18 inches half the width of the roll.
In australia they actually call this stage the lock up while the interior trim work is called a fix.
Drying in for better lack of a term is making a house impervious to the rain or short for dry inside.
In short drying in a structure means that the roof has been protected with at least a layer of felt a product like tyvek housewrap has been installed along with all the windows and doors.