A van containing a 3D printer arrives at your front curb, the plumber knocks and, granted entrance, checks your sink downspout, which is leaking. Problem identified, she calls up the broken part on her computer and prints it in the van, installs the new downspout, and finishes the job. No inventory to carry around, just a focus on service. Amazon received a patent this week that supports this scenario. The human is the critical factor here, as they translate the customer’s issue into a plan, identify the broken or missing parts, print them (though this is a machine’s job), then installs it.