These tool holders are designed for 0.5in (½) and 0.375in (3/8) neodymium magnets. They will require supports for the hook. For a good fit in the peg holes, I don't clean the supports completely which leaves a bit more friction. Whittle down if it's a bit too tight.
Glue the magnets in, they can work themselves loose if not bonded.
If you use neodymium magnets, you can expect ferrous tools of significant size to hold on the larger ones. I was able to hang a cable stripper plier. YMMV.
The author marked this model as their own original creation.