As stated before, I used blemished longboards for my shelves. I happen to work at www.TheLongboardStore.com
, so I had access to several for cheap. You however, will more than likely not have this can of luck, so you will have to make your own or buy pre-made shelves. If you are ambitious enough to make your own, then you shouldn't need me explaining to you how to do it. Get some wood and get to it.
For those looking for an easier route or don't have the tools to make their own, pre made shelves can be bought from places like Lowes or Home Depot for relatively cheap. You'll find them in the closet organization section of the store. They usually come in a range of colors, so at least you aren't stuck with some ugly color you hate.
On to the holes. The boards I used already had holes drilled in them for mounting the longboard trucks, so I used those to run the cable through. One modification had to be made though and that was drill a 1/4" deep by 3/8" diameter hole into the bottom of the boards for the shaft collar to fit up into. This creates a nice flush bottom with nothing sticking out of the bottom of the shelf. The location of these holes will vary a bit depending on the size of your shelves, but I recommend putting them at least a 1/2" in from any sides and as wide ass possible for the best stability.
To do this, I used the aforementioned 3/8" Forstner bit. A Forstner bit for those who don't know creates a flat bottomed hole, unlike a regular drill bit. I used a drill press to drill all of these holes, but a hand drill could be used.
Since there were already holes in my boards, I was done. But for you, you will need to drill the rest of the way through the board so the cable can pass through. Use a 3/16" drill and place a block of wood under the shelf in the spot where you are drilling. This will keep the wood from splitting out when the drill breaks through the other side.
Final thing to do is give them a good sanding (unless they are pre-made and already have a finish) to remove any splinters or rough edges. This also prepares them for staining.