The new KV10 LED fence tester has no wires and no need to earth. Simply hook on to the fence to get a clear indication of the current being carried.
 
The Hotline Fence Tester is a handheld self-earthing fence tester with bright LED display that is capable of Reads up to 10 kilovolts (kv). Very handy if you want to check a fence, without the risk of trying it yourself!