These are traditional cutlers rivets. To use them, pound the male solid shank side into the female tube side and they will hold tight. Really tight. This style handle fastener is still widely used today after a hundred or more years because it works so well. It’s quick, easy and holds fast. Your commercial kitchen knives almost certainly use some form of cutlers rivets. This Cutlers rivet will fit a knife handle stack (2 scales and tang) that is .60” thick up to .95” thick when countersunk. This is going to cover nearly every knife handle thickness in your kitchen and most hunting knives. Tip: You can counter sink the heads or leave them proud. It has been done both ways historically but certainly countersunk is more widely used. To countersink the heads, trial and error drilling into your handle material until the head is flush or even below the surface and sand down the handle material flush to the head. The countersink hole bottom does not have to be flat. If you want a flat bottomed hole, grind the tip of a ¼” drill bit flat. It will cut enough to get the job done. You are only countersinking this .045” Tip: Try not to undersize the hole in wood or other natural material. When you pound these together the shank is going to expand putting pressure on the wood and over time the wood is going to crack from humidity changes. Wood always loses. G10, Micarta or other high pressure laminate or phenolic don’t change size so much and are quite a bit tougher so this is less of a concern. Better to have the shank hole a little oversize than undersized. It’s OK to use epoxy with these to seal the scale but it isn’t required.