A type of multi-tasking which involves one person, man or woman, jacking off four guys at the same time, while they stand tip to tip, two on either side.
Variation 1: Choo-choo technique. Two dicks in your left hand (tip to tip) and two dicks in your right hand (tip to tip). Right and left hands articulating as a locomotive. Also known as Quattro-Loco.
Variation 2: Downhill. Both hands move simultaneously in an upward to downward
motion,
like a downhill skier.
Variation 3: Uphill. Both hands move simultaneously in a downward to upward
motion,
like a backwards skier.
Other variations left to your imagination.