3 Part Technique - The Guillotine Choke vs Half Guard or vs Side Control has a subtle, but important detail, in terms of the depth in which the choke in locked around the neck: Your choking forearm doesn't go underneath the chin to crush the windpipe, rather it is placed along the side of the neck to attack the carotid arteries. The other side of the neck is pressed against by the mid to bottom part of your ribcage. While in your opponent's half, if at any point he begins looking to transition to deep half or use his underhook, create some space between your chests, and wrap your arm around his head while dropping your side on his neck. At the very least, he will become preoccupied with defending the submission and allow you to easily pass, or even submit to the squeeze afterward. If he attempts to reverse you by bumping you over onto your back, escape your hip so you may shelf your elbow on his shoulder and finish. If he tries to pull you over him to escape, mount on top of him and brace yourself with your forehead. In either case, make sure to deepen your choke from the shallow positioning used to finish from Side Control, to that used while finishing from mount or from guard.