A few people on fb seem to find this interesting so I’ll throw it in here.
It’s a method for using solids and outershell to create a ‘mask’ that you can intersect with a face, this produces a complex single shape that doesn’t need a whole bunch of edges cleaned up to make it one face.
By the way, I have a FB persona ‘Box Says’ simply so I can respond in situations where the Box page itself can’t. Anyone who has asked to friend it shouldn’t be offended if I haven’t responded, I generally don’t see them and it doesn’t friend anyone.