The frame of the tensioner ist bolted to the x-gantry. That makes it stiffer and it fits better to the aluminium bar. It also doesn't twist while the printer is moving along the x-axis.
1x DIN M8 Screw 30mm or longer
1x DIN M8 Nut
1x DIN M3 Screw 30mm
1x DIN M3 Nut
The author hasn't provided the model origin yet.