Call it a "hearing hole". The idea is to project sound to the player. When you are playing in a jam with a group of ukulele players it is hard to hear yourself. Side sound ports help a lot. I put them in all my instruments except for the Pinecones. Here is how you do it.
I scribe a pencil mark where I want the hole and then rough it out with a Dremel drill bit. I am preparing to fit in, the wooden oval you see a lower right.
The oval hole is perfected with a small sanding disk on the Dremel until the wooden ring just fits, then it is fixed in place with super glue.
It didn't take long before both ukes had their side sound ports. Now some trimming and sanding is called for.
With the sound ports in its time to box em up.
Floyd's uke gets its back.
I like to add a few barrel clamps to insure a good tight fit.
Caroline's uke will get its back tomorrow when the clamps are freed up.