Overlocker

I managed to thread it and get it working. Now I need to get used to it. I think the tension might need adjustment.  
An overlocker sews the edges of fabrics, cutting off the excess fabric at the edge of the garment.  It neatens hems so no other finishing is required.  
When you first start using an overlocker it is suggested that you thread it with 4 different colours so it is easier to trace the threads through the machine.  Also so you know which threads may be too tight or too loose so you know which tension knob to adjust.