A jackknife tie is a bondage position in which the captive's body is held bent in half like a jackknife. To achieve this, the legs are tied together at the knees and ankles, the wrists are tied together and then the captive bends at the waist and has the wrists and ankles fastened together.
Often the elbows are tied together too, and there could be a rope around the elbows and knees. This makes it more difficult for the captive to bend his or her knees, restricting mobility or the possibility of bringing the hands near the face (to use teeth to untie knots, or remove a blindfold or gag).
The captive may be further immobilised by laying them on their back and then fixing a rope between the ankle ties and a hook on the ceiling.