As a newbie to instrument-making, I had four or five sets of feeler gauges around the shop. Most were incomplete as I'd scavenged individual gauges to use as shims. I also noted that whenever I saw a luthier using a feeler gauge, it was loose - not being held in the pocket-knife-like stack in which they're sold.
Some years ago I made a holder for my 1-2-3 blocks and brass setup bars as shown in the pic below, and decided I needed something similar to organize my feeler gauges so I wouldn't have to remove and replace them from the post, or worse yet, have them loose in a drawer somewhere so I'd have the devil's own time finding a specific size.
I cobbled together the holder shown in the second pic below from some sappy cherry I had in the stash. I used a rip blade that cuts a flat-bottom kerf to cut 9/16" slots into the stock. The blade was a scrunch over 1/8", so I just cut a slot and moved the fence over by 1/4" and cut the next slot. Whacked off three pieces about 2 3/4" long from the resulting board, glued them together with some 1/4" MDF on the open side and the bottom, slopped some BLO over the whole thing, and Bob's your uncle...
There are 12 slots per row, so I know that the front row ranges (left-to-right) from .001 to .012, the second from .013 to .024, and the third from .025 to .035
