Starting a new thread with some valuable information I learned in the process of installing my end wedge, might save someone some time
I also added part of this as a response in another thread.After cutting the channel with a Japanese saw and chiseling out the waste, I took a 6" steel engineer's square, and just stuck some 3M 80 grit self adhesive paper to it and trimmed to the edges, then ran that back and forth on its side against the channel wall. Watch for a tiny little ridge of saw dust piling up along the edge. When there is an equal thin line of dust across the edge, then its square. Repeat on the other side.
I then took a blank that was cut the same as my wedge, put the self-stick on there, and evened up the bottom of the channel.
on measuring my ivoroid blank, I drew a centerline along one of the grooves. i used my caliper to measure the top of the channel and the bottom of the channel (in thousandths) and recorded those values. I then determined half the value for each, then again use the caliper to make marks at the top and bottom of the wedge at exactly half the distance on either side of the centerline.
Planed to the lines and straighted up on sandpaper, and this wedge fits in there with no gaps that are even visible under magnification. I am continually astonished at the level of accuracy i get by using a caliper, I now use it almost exclusively for any measurement under 4"