Complete Butterfly Guard, Vol 2: When They Deny the Under-Hook
Marcelo's jab-mentality answers when the under-hook isn't available: collar-tie and triceps cups as one-beat sweeps, the straight armbar when they post to defend, the snap-and-pull guillotine off a fake lift, and the double-overhook clamp that sweeps either direction with one grip.
This public BJJ flow maps techniques and transitions.