These insulators are to screw in to wooden fenceposts and will hold twine, wire, polyrope (up to 6mm diameter) and polytape (up to 40mm diameter).

The beauty of these is that when they're in position and the tape, rope,etc is slotted in the top, the top holding clasp is brought down to hold the conductor TIGHT in position. Even if one part of the fence breaks, you can be assured that the conductor is held firmly in place throughout the rest of the fence and not trailing on he ground. I've installed these on many fences and am amazed at how well they keep a fence line secure thoughout the year in all weathers. Perfect if you're installing a permanent fence and you want something of this calibre.