When they get going everything happens at once.

The internal doors started going in today. They go in rigged with the French equivalent of sky hooks, then the plasterer gets going with his internal wall terracotta blocks. The door people put screws into the outside of the frames in a v-shape (you can just see this on the right hand side of the door frame. The plasterer then incorporates those into his wall leaving no visible evidence of door fixings in the frame.

Another little trick is his use of string! There is a square section device jammed up against the wall on the left and another one skulking behind the door frame. Each has a piece of string from top to bottom. In order to give himself a line to work to another piece with slip-knots on either end is stretched horizontally between the vertical strings. This just gets slid up with each course - devilishly clever!
The door frame shown is from the kitchen, this side, to my lair the far side of which, when built, will be the wall to our bedroom at the far end.
Confused yet?