These monofilament tighteners are used to easily tighten our deer fence monofilament wire for best results installing our deer fencing properly. Each monofilament tightener is ultra-violet (UV) treated for increased longevity. We recommend using two monofilament tighteners between each corner of your fencing project, one each for the top and bottom monofilament wires. You will need our monofilament tightener tool to properly operate these monofilament tighteners. .