This device can be used to lock a plastic or metal wire. Using all plastic is safer if there are any live parts in proximity. The device can be used also with metal wire.
Usage is seen in the picture: Put the wire trough holes and turn the device 1 to 2 turns. For plastic use thin 1.5 mm string trimmer line. To good grip do 2 turns. For metal wire copper is recommended only one turn is normally enough for good grip.
Use always with appropriate warning sign because the device or wire is nor unbreakable.