Fortunately we have three dimensional tools which we've used since the 777 program and much more recently some kind of VR-like tools we used on the 737 MAX which help with this. But even today sometimes a physical mockup is of amazing value in figuring out if folks can reach places either to put the airplane together in the first place or to fix it later.....

(I guess even though I've been retired for over a year I still feel like saying "we"....for some portions of the 777 and later the 737 Next Gen part of my particular responsibility was getting folks together each week and "flying thru" the 3D and helping them sort out spatial stuff including maintenance access.)

__________________
Bernard Cawley
NAR 89040 L1 - Life Member
SAM 0061
AMA 42160
KG7AIE