I'm going to remove the sling swivel studs from the CZ 455 rifle that I'm setting up for bench rest shooting.

What does one use to fill the holes left by the vacant studs?

Thank you.

Plastic or wood stock?

Plastic - perhaps something like JB Weld or Bondo. You may have to repaint afterward.

Wood - wood filler. You're probably going to have to refinish. Minwax does make putty for repair of finished woods, so you might get lucky there.

Alternatively, if the screw holes aren't bothering anything just leave them alone or cover them with some duck tape or something.

Wood stock.

Go to a hardware store (or section of a big box store) and get some very small plastic button inserts. It will leave the 'threads' intact and you won't have to gouge out the filler material if you decide to sell and want to put the studs back in the stock. A bit of some removable adhesive can be used if the 'buttons' are too lose. Otherwise do as suggested per previous replies.