VIDEO HERE (4:21 minutes)
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That's a good tip for somebody that's never backed a trailer, but what the gentleman fails to mention is the closer the trailer axle is to your hitch, the harder it is to back that trailer up without jackknifing it or having to pull forward time after time to straighten the trailer out.
Seriously, check out videos of how easily a semi can back a trailer in to some incredibly tight spots sometime, then look at how far back the trailer wheels are from the hitch.
I can back a trailer for a 12 foot boat like it was second nature, but I can't back my 8 foot cargo trailer more than 10 feet without it heading off in a different direction like it had a mind of its own.