When I am sanding or finishing flat surfaces I find I like to have a light source that is just right on the surface and nearly parallel. This device allows an LCD light source to be parallel to the light source or shifted by eight different slight angles. (±1½°, ±3°, ±4½°, ±6°). This example is done with increments of 1½°, but you can make yours to the angles that you desire. It is done by cutting 2" square tubing at precise compound angles.
Step 1: First Cut
To make this you will need 2", ⅛" thick walled square steel tubing. Make sure it is steal and will attract a magnetic. To cut the steel I used an abrasive cutoff wheel in my 10" miter saw. Here is a good source for any size cutoff wheel you may need.
Zoro is a good place for makers to find the stuff you need. Shipping is only $5 for orders below $40. Above that amount and shipping is free.
Set your saw to cut 3° across the tube's top and 1½° along its side. If you have a compound miter saw this a trivial. Since I only have a normal miter saw I made a 1½° wedge to hold the square tube at the correct angle.
Step 2: Second Cut
Mark 3" on the tube and set your saw to cut 6° across the top and 4½° along the side. You have finished the cuts. Now if you want to make other just measure 3" and use the cut with the angles from Step 1. Alternate steps to cut angles until you have cut as many as you wish.
Step 3: Clean Up
Use a sander and files to smooth out any rough edges. I like to use a sander to give all four faces a nice grained finish. When done apply a coat of paste wax
Step 4: Light Source
These light are available many places. They are 3¾" tall, 2½" wide, 1⅜" thick, and have a magnet on the middle of the back. It makes it perfect to use with this incident gauge.
Although widely available, at Harbor Freight they are given out for free to induce people to come into the store.
So whenever I go to Harbor Freight to buy something, I bring a coupon for 20% fpr the item I am buying and another coupon for this free light.