Marcelo Garcia Complete Butterfly Guard Vol 1: Classic Sweep
Marcelo Garcia's butterfly cover rules and classic sweep: underhook to the bicep, push the elbow in, scoop and rotate, plus the reshoot and two-on-one. The three cover rules are hands before feet, shoulder pointed, and elbows tucked, and every other attack in the series branches from this sweep.
This public BJJ flow maps techniques and transitions.