Emphasis with this drill was to preemptively break down opponent's butterfly guard before he can totally sink in hooks and posture up for clinch. This is done by forcing both of the opponent's knees down to one side breaking his posture while simultaneously controlling opponent's bottom leg and reaching up to underhook opponent's neck for collar tie. One knee should be past opponent's guard and pinned against opponent's side while with a large step back your trailing leg escapes opponent's half-guard or whatever entanglement. Then sit back in for side control or kesa gatame.
Edit: if trailig leg is caught in OP's half guard, be certain to shoulder cross face with maximum pressure while breaking the half guard.
