two ears 66 and 68 extend along substantially the entire length of the clamp 50 the two ears 66 and 68 form together with the attached vent bar 34 a pair of parallel grooves 67 and 69 that extend along a common length of the vent bar 34 and the clamp 50 the t shaped cross section of the clamp 50 supports a sliding fit with the elongated channel 16 the elongated channels 16 and 18 of the sash 12 and window frame 14 are intended for mounting window hardware such as may be consistent with so called u201c euro groove u201d systems the channel 16 has a bottom 70 and two sidewalls 72 and 74 with overhanging rails 76 and 78 the center section 64 of the clamp 50 extends between the overhanging rails 76 and 78 and the two ears 66 and 68 extend beneath the overhanging rails 76 and 78 as shown in fig1 and 2 the sash 12 together with its elongated channel 16 can be aligned with the clamp 50 projecting from the vent bar 34 for sliding the clamp 50 along the elongated channel 16 to a desired position for mounting the sash 12 within the frame 14 for adjusting the mounting location of the vent bar 34 with respect to the sash 12 the screws 52 and 54 are loosely held in engagement with threaded holes 82 and 84 of the clamp 50 a setscrew 86 an extension fastener which engages a mating threaded opening 88 in the clamp 50 is accessible through an aligned opening 92 in the vent bar 34 the setscrew 86 can be turned into frictional engagement with the bottom 70.