This might be a good exercise for someone just learning to draw or sketch. Not drawing every little thing in the shed, but several things from it anyway.
It seems to me he could just draw a particular thing ONCE, and then put a number next to it for how there are.
So his grandfather doesn’t really have a 100,000 things in there per se, but if he’s got, say 4 1 lb. boxes of 5 penny nails, you don’t need to all 3,000 nails, but 1 5 penny nail could represent all of them.
Same with all the identical bolts, pins, screws, nuts, washers, connectors, hooks, etc., etc.