I'm sure as DIY'ers you have considered making garage tool storage neater and the dowel rod idea certainly isn't unique by any stretch. So if you are new to DIY and you go the the store to buy wooden dowel rod to make this fine project you may select 3/8", 7/16" or possibly 1/2" diameter rod as the appropriate size. OK, I got a new drill bit set for Christmas with all those sizes and I'm ready to get-er done.
So you get home with these dowels selected, choose the appropriate bit, bore a hole at a gusstimated angle in that fine piece of lumber rather than a scrap piece, and low and behold those stupid dowels are loosie as a goose. No amount of glue will work and make a satisfactory fit and even a non-seasoned wood worker would know that. Then I discover those dowels aren't even round like they look either.
So don't despair, all isn't lost if you have a spade bit of that size selected for the holes. No it probably wasn't in the Christmas gift set.
I have a good set of spades and a not so good set. I choose the not so good to re-size to fit the under size dowels that have shrunk in diameter because the dowel rods were machined when they were green and have dried out smaller and of round. For this project let's not pay much attention to Out OF Round, OK.
Now to the trusty bench grinder to make a spade bit bore a smaller hole. Yep, a few thousandths off each side, it's possible and a common practice. I've read it can be done with a file but I haven't tried that being my grinder is handy.