I'm pretty certain this has been done before, but with Christmas coming and with gift cards being last minute gifts, I thought I'd do some gift card holders,
one is done in poplar, the other, walnut.
There are two pieces to the holder, each 0.1875 thick with a pocket milled in one piece (0.003 deeper than the thickness of the card to accommodate the different thicknesses
of various cards. This way if it's too loose, I can fine tune it by just sanding the adjacent sides), then glued together. Sanded with a couple coats of semi-gloss poly.