I wonder if anyone can help here. Had a nozzle blockage so removed the nozzle and cleared that, no issues there. But on reassembling I noticed the heater block appeared loose and rotates. I managed to fit the nozzle OK but can't figure out how the heater block is secured? I've removed the extruder assembly from the carriage and found the set screw at the rear, that appears tight and it seems that the heater block is loose on the small piece that connects it to the horizontal bar. How is the heater block secured to that? I can rotate it clockwise and anticlockwise within the limits of the attached heater and thermistor cables and it doesn't feel like it's tightening. Is this piece threaded?

Confused!!