As I was rolling with my instructor we were starting from our knees and I tried to get him in a guillotine. As I pulled his body towards mine and began to apply the move he lifted his head up quickly and you can imagine what happened next. My chin hit square into the back of his head and it was a bloody mess. Suprisingly enough I was not bleeding and he was the one with a big gash on his head. Just a warning to you (I know you might know this) make sure your head is to the side of the individual when applying the guillotine and wair a mouthpeice, even if in practice.