Steve, That's actually EASY to do! Most anywhere you're going to need a "grommet" - one of the sides will NOT BE SEEN. A wooden one as you have described is simple in whatever shape you desire. Just make the part(s) (one with holes & one blank) and position an oversized piece of 1/4" MDF, etc. on the back. Ideally, you will make matching backer boards, as well - with each one having matching (small) screw holes - so that the obsolete one may be removed and the blank be installed - using the same (small) screws and holes.
This reminds me of something funny that I recently observed...I am very near completion of my new office desk for computer setup and reference table. It is 14'-3" long and 34" front-to-back. No legs, yet very sturdy - using a double cantilever design that my Dad taught me many years ago. There are electrical outlets below this desk, and I wanted the appearance and functionality to be perfect. I drilled 3- 1.25" diameter holes about 4 feet apart for grommet installation. I often utilize this size of grommets. Normally, I have several "on hand", but I had depleted my reserves - so I had them on my list for next shopping trip.
A few days later, Joy (my wife) and I went out for dinner and were very near a Home Depot in Lawrenceville, GA. An old man walked me to electrical and then to their selection of grommets. He offered black and white, plastic and metal. I told him black, plastic, 1.25" diameter - going through 3/4" plywood. The grommets he handed me looked perfect, but they were in a plastic bag. There was something curious about them - they were ONE-PIECE! I asked if he had an open bag of those grommets? He said, "No - let's just open this bag!" He then handed me one, and as I suspected; they were ONE PIECE!
If this isn't comical to anyone reading this, picture this potential scenario: I have 3- 1.25" diameter holes. The grommets are ONE PIECE! I put the grommets in-place (they each have one 3/8" diameter hole molded into the top). How on earth am I supposed to get a male or female end of an electrical cord through a hole 3/8" diameter? His answer was: "No problem - just cut-off one end of the cord, slip it through the hole and REATTACH the end of the cord!" It was all I could do to contain my laughter until I was out of his line of sight.
We then went to Lowes, where their 1.25" grommets were TWO-PIECES! Now, I do not have to cut the ends off of my new computer cabling! Hallelujah!
Otis Guillebeau from Auburn, Georgia
OPG3 Tweak everything!