My son-in-law earned a MacGyver badge not long ago. Went ATV riding at 5.am. to beat the desert heat. Both ATVs on his SUV/trailer (but usually I take my Jeep/trailer). Roll my ATV off the trailer. It won't turn over. Dead battery (even though I rode it onto the trailer under power 45 minutes earlier). My jumpers are at home ... in the Jeep ... he has none.

About ready to head back home, until he got the bright idea to pull the heavy-gauge wire off the after-market sub-woofer he'd recently installed in his SUV. Ergo! Emergency jumpers.
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"Things that have never happened before happen all the time." — Scott Sagan, The Limits of Safety