Either during sex at orgasm or while your 'one night stand' is asleep.
the idea is you cum and shit all over your partner at the same time giving you and your partner your weird sexual jollys. if your partner is asleep then you do the same process without waking her up and leave her alone in her house/flat, so she wakes up with shit and cum all over her body, make sure you give her a fake name so she cant track you down.

When you assist your partner in jacking off.

Jacking off your Boyfriend the same time he masturbate.

A shooter that is made of 1/2 yukon jack, 1/2 jack daniels

When you accidentally plug two banana plugs into the same hole. Other wise known as the mating ritual of the consenting adult banana jack.

When you get a handjob from two hookers while doing cocaine

See Double Jack For Definition
Exact same Idea As The Double Jack But Instead Of Shiting On The Partner You Do The Same But When You Have Diarrhea!
Some Would Say This Is Sick But Oh Well!
See Yah!

When you take your penis back and forth between a girls tits. AKA Titty Fucking