Reply by sikrap

Well, it turns out that I lied. The magnet are 3/8”. All you do is clamp the mdf down and drill 4 holes with a forstner bit, drop a drop of epoxy in, drop the magnets in until they’re flush with the mdf and you’re good to go. You’ll be amazed at how securely these itty bitty magnets will hold a plane iron and how much easier this simple jig makes flattening/polishing the back.

Well, I’ve tried several times to upload the pics, but it just ain’t working for me. PM me with your email address and I’ll send them to you

-- Dave, Colonie, NY