kata-te-jime
(single hand necklock)

"From kami-shiho-gatame, Tori releases his hold on Uke's belt and takes a hold of Uke's collar. With his thumb inside the collar and from the left side, as close as possible to his right hand (against Uke's left ear) .
At this moment Tori's left elbow is passed from the leftt side of Uke's head to the right and advances as much as possible against Uke's right shoulder, in a guillotine movement.The hold is applied."