Cotter pins are used to attach the wire to the post. In the photo below, you can see that the tails of the cotter pin are wrapped around the post and not around the wire. If you do bring the cotter pin tail back around the wire, do not cinch it up tight. This is to make sure that the fence wire has free travel thru the pin. We have observed that it often does get cinched up too tight and when the post bends with pressure from tree limbs, wildlife, etc, that the binding of the wire in the cotter pin does not allow for the post to return upright.
The cotter pin we sell is 13 gauge, class III. You want to drill a hole that just allows the pin to go through. Do NOT oversize the hole. A 7/32″ or 3/16″ hole is adequate, so please don’t drill a larger hole. If you have some 10 to 12 gauge cotter pins on hand, please just keep them for other uses, and do not use them on PasturePro posts.
Making your own cotter pins out of 12.5 gauge hi-tensile wire? That would be acceptable. My ol’ friend Willy Kilmer has done this for years – he calls his a diaper pin knot. In this case you will only need to drill a small hole to allow a single 12.5 gauge wire to pass thru. Just remember to not lock the fence wire in place – make a loose knot to allow free travel of the fence wire.
I have done this before but personally prefer the manufactured cotter pins as my hands get weary after working with the stiffer hi-tensile wire, making and installing cotter pins all day. (Maybe that’s a sign of my age.) To me, the pins we provide are easy to work with and too cheap to make me want to make my own!
We hope the above guidelines are helpful to you, and if you have any specific questions or comments, please feel free to call us anytime.