clamping bars comprise a plurality of continuous threaded bores running essentially perpendicular to the clamping bars said bores being enlarged to a predetermined nominal diameter and said bores being adapted to selectively receive a clamping screw application_number US 75115891 A description according to the schematic view shown in fig1 a rectangular frame is provided which is generally designated with reference numeral 1 the rectangular frame 1 is fastened to the not shown work table of a machining tool by not shown fixing means the rectangular frame 1 comprises two transverse frame members 2 and 3 as well as two longitudinal frame members 4 and 5 the frame members 2 and 3 and the frame members 4 and together form a rigid rectangular frame structure the two longitudinal frame members 4 and 5 are provided with threaded bores 6 equidistantly arranged in a row extending along the length of the frame members 4 and 5 said threaded bores 6 run in a direction perpendicular to the plane of the rectangular frame 1 in the embodiment shown in fig1 the rectangular frame 1 is provided on the one hand with two clamping bars 7 and 8 and on the other hand with two clamping bars 107 and 108 the design of these clamping bars is shown in detail in fig2 to 4 and 6 and 7 respectively whereby as an example the clamping bar 7 is shown in a lateral view in fig2 and in a bottom view in fig3 and in a partial sectional view in fig4 the clamping bar 107 as an example is shown in detail in fig6 to 8 first the following description of the clamping bars particularly refers to the clamping bar 7 however it is understood that the following description also refers to the design of.