The instrument has an inside diameter suitable for a normal gripper etc. There is a tip notch for the thread and a longways slot for needle withdrawal from the sleeve for the thread to be pulled tight and the knot placed. The instrument has markings on its exterior for thread lengthing and looping during knotting, and the tip notch runs crossways to locate the thread and forms here a cavity to take the gripper tool. The end of the instrument is thickened out to allow it to be gripped in the knot-tightening stage. The inner sleeve springs totally back into the outer sleeve while retaining sufficient diameter for the gripper insertion.
