I think this may be a jig/fixture question. I am not really interested in making a whole lot of these but it would involve making a whole lot of cuts to make one.
Here is a picture of the part I am going to describe:
You can see it in use on this page: Backstrap Weaving – What IS backstrap weaving? « Backstrap Weaving
For scale they are about 24" long in the first image. What you see amounts to a giant comb. It is referred to as a rigid heddle or a reed. Originally these were probably made by lashing many basket reeds together and burning a hole through the centers of each of them. In weaving (simplified) a thread either goes between two reeds or in the center hole of a single reed. When this is done, every other one, then lifting or lowering the reed will separate the threads so that you can pass threads between them in one motion as opposed to doing the over-under-over-under thing. Depending on the size of your thread/yard will determine the pitch you want to use. Common sizes are between 6 and 12 dpi (dents per inch).
I have played with some ideas, some of which are good, others are bad. Up to this point, the major idea is to do this on the table saw with a jig somewhat like a box/finger joint jig. The idea being that I would take a piece of wood/masonite cut to final size and glue two boarder boards top and bottom. When the glue was dry and set, I would box joint it with the initial board face down. I would set the blade height to just pass through the initial wood and not into the boarder boards. When completed I would glue on 2 more boarder boards opposite the existing ones to sandwich it. I like this idea except that limits me to the width of my saw blade, and it depends on a surface glue joint (scary especially if I were to use Masonite). Many of these appear to be made from plastic, likely injection molded and probably done in china at some ridiculous low price. However, I would like to do it myself regardless of cost.
I have seen smaller ones of these (tape looms) made with a comb saw, and I have seen other hand tool methods for doing these tool, but I neither have these tools not the patience/discipline to manually do 216 of these cuts by hand
If I could do this in Masonite as a single piece, with consistent indexed cuts that would be great! I know I can simply set up a perimeter to handle the stop cuts, but what would be the best way to accurately and repeatably index a straight cut? I assume if I can come up with a way to do the long cuts, the centered holes would be something similar.
Each reed in the system should be 3 times the size of the hole in the middle and the space between them. So if i wanted to work with 1/8" cuts I would have 4 dpi. To get to 8 dpi I need to deal with 1/16. For an example there would be a groove 1/16 wide, followed by 3/16 of solidness with a 1/16" hole in the center, followed by a 1/16" groove and so on down the line. One can quickly see the tedium involved in doing this manually or without a jig.