Answer: When you shove multiple automotive parts into one.
In this case I was trying to carry some Ford GT belly pans home, along with some large interior panels, and the only vehicle available was our long-term Hyundai Genesis.
But as my older brother is fond of saying at such times: "Ahhh, it'll work."
And he was right. Despite lacking a fold-down rear seat (it does have a pass-through) I was able to get the larger interior panels in the trunk and the belly pans in the rear seat. The trunk lid's hinges are effectively designed to have minimal intrusion into the trunk area. I also used rags on the edges of the belly pans to keep them from marring the Genesis' leather surfaces. Despite being a rather wide car the pans barely fit in the rear seat, and only after placing them at a creative angle.
But don't try this unless you're an expert at making sedans act like utility vehicles. For example, here's a shot of our former long-term Chevy Malibu (which does have a fold-down rear seat) carrying four pieces of 8-foot lumbar last weekend. It was also hauling two kids at the time. Necessity is the mother of invention.
Karl Brauer, Edmunds.com Editor in Chief

firstwagon says:
01:52 PM, 06/25/09
Life is so much easier with a wagon.
drunkenpanda says:
02:06 PM, 06/25/09
I once got 2 4*8 beams and 4 2*4 boards into my Camry with the seats down. Someone cut me off and all the wood smashed into my headunit. Only damage was a cracked preset 2 button.
stephen987 says:
02:19 PM, 06/25/09
That's nothing. I fit 34 cinderblocks into my '82 Accord hatchback. The noise was horrible as the mudflaps scraped along the Tennessee pavement.
merkava5 says:
03:12 PM, 06/25/09
It's true, what firstwagon says.
I've been consistently (and happily) surprised by what my WRX wagon can hold. Lumber, furniture, endless rubbermaid totes, heck I even took home a special order of 30"x40" casement windows from the home improvement store. There were six of them!
n_tesla says:
03:15 PM, 06/25/09
I know someone that put a kayak inside their Lexus branded Land Cruiser. It "almost" fit so they slammed the tailgate which pushed the kayak forward and the windshield onto the hood.
Doh!
cartester16 says:
04:05 PM, 06/25/09
BMW E46 Wagon. Perfect car. Period.
dougtheeng says:
06:04 AM, 06/26/09
No folding rear seats on the Genesis? Thats disappointing. I know the G8 gets burned for this, so I think its fair to point out that its missing on the Genesis too.
deagle13 says:
09:13 AM, 06/26/09
So Karl, have you accumulated enough parts to build a second GT yet?