No need to add a Horn insert for arrows shot from a 45# Bow,just wrap your Linen under the Nock to strengthen it.Personally i alway's add the Horn Sliver's no matter what strength bow there intended for,it's not necessary but i like to do it.
The Horn 'Sliver's' supplied by Richard Head i find too thick and too short,it's better to buy the larger flat sections of Horn'i think he sells it..?I like the Horn to be 2" Long and 1-2mm thick,but to each his own
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Tools i use for adding the Inserts,
Japanese Saw or a Backsaw to make the cut.
These tools are good for getting a nice thin straight line as the saw only cuts one way,allthough you can buy a Jig if you want.
Araldite two part epoxy or a good quality Super Glue to bond the Horn to the wood.
24hrs drying time for the Epoxy or a couple of Hours with the super glue.
Emory Cloth to tidy up or you can use a file and sandpaper.
I also wrap thread under the Nock,you can never be too carefull!