The roof sheathing is installed and a roof covering permanent or suitable reliable temporary roof waterproof.
Roof dry in.
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.
Roof dry in flashing and underlayment.
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.
Drying in for better lack of a term is making a house impervious to the rain or short for dry inside.
March 7 2020.
In australia they actually call this stage the lock up while the interior trim work is called a fix.