@writingslowly For boxes of this size and type 3x5" are far easier to come by. In the 6+ months I've been watching various searches I have yet to see one of these for 4x6" cards. (I'm half tempted to buy a 3x5 box, cannibalize the hardware and build a 4x6" box. 4x6" boxes are easier to find in wood in larger 4-6 drawer form factors or much more ubiquitous in the metal multi-drawer (2 or 3 drawers) stackable form factors from mid-century to the late 70s. For more options, see The Ultimate Guide to Zettelkasten Index Card Storage .