Gripple Wire Tensioner with clip, perfect to be used with Polywire.  Made by Gripple, to fasten to fence or posts.
 
Easy to apply tension by hand or by using Gripple Torque Tensioner Tool (sold separately).
 
Fits wire 1.88mm (0.04") to 3.00mm (0.12")
Max capacity 400 kg (818.8lb)