to fig5 there is shown a top view of an inner jaw portion 12 whereas fig6 shows a similar view on a corresponding outer jaw portion 11 it is clear that each jaw portion 11 or 12 of any clamping assembly 20 30 according to the invention comprises three differently sized grooves 51 52 and 53 respectively the longitudinal axes of these grooves 51 52 and 53 are oriented in an angle of 60 degree one to another however these angles of 60 degree are not mandatory it is only necessary that the total internal angle of the triangle provided by these three grooves 51 52 and 53 is 180 degrees the grooves are also in the same median plane which indicates that only one pin screw or rod can usually be introduced in one of the grooves 51 52 or 53 and such an introduction blocks the other empty grooves it is an aim of this orientation to provide a simpler mounting of a fixation device since based on the chosen pin or screw a clamp of the invention can be chosen and through rotation of the clamping assembly the correct sized reception cavities 71 72 or 73 is usable for a well clamped connection wherein the clipping of the pin.