As I said in a previous post I am ding a plumbing job here at home.
I am a one man show and it is on the first story. So to cut the pipes going through the walls is quite an issue,
Up on the ladder on the out side, set the pipe to stick out just far enough so a wall clip will fit and enough pipe to go into the solder on fitting.
Then down the ladder, up the steps to the inside and mark the pipe, being very careful not to move it in the whole process or it can be scrap.
Make up a gauge using some scrap to imitate the final joint. Paint it nice and white so you can clearly see the markings and the simply stick it through the wall now you gave all the time in the world to go to the inside and apply a bit of pulling force to ensure the wall clamp is snug against the outside wall and make a mark where you need to cut the ACTUAL pipe.
Here you can see the mock up elbow and a wall clamp of which I had removed the part that will go into the wall.
Easy to mark on the inside. By the way all the walls are a little different in thickness, Some are not plastered and some have tiles already fitted.
and then a simple job of cutting to length.