US Patent # 7421798
I have one and it is super great for setting angles, don’t know how I got along without it before.
Call: 1 (209) 835-1626
eMail: miterset@comcast.net

Figure 1
Adjusting your miter gauge in .5° increments is where the detent bar comes into use. (Figure 1) shows the detent bar and the value of each machined step. The 1° step and the 2° step are stamped on each side of the detent bar. The increments of .5°, 1.5°, 2.5°, have been purposely left off. The idea is that they would clutter the bar and it would become confusing for the user.
“Setting a 22.5° Angle”
View this video for a first hand view of the Detent Bar in Use
If Video fails please, visit this site.

Figure 2
The detent bar is a device that allows you to shift the adjustment either plus or minus 2.5°. Remember, the pin holes are 5° apart so the ability to shift the setting up to +2.5° or –2.5° will give you the full range of adjustment. Lets say that you need to adjust your miter gauge for an 11° cut (figure 2). Notice the pin location is at 10° and the pivot pin is at 00. Now I add 1° by placing the detent bar against the pins with the 1° detent against the pin in the 10° hole and the opposing end against the 00 Pivot hole.

Figure 3
See close up of the placement of the detent bar against the 10° pin (figure 3).

Figure 4
Now notice that I have the miter gauge against both pins ready to tighten, and make my cut of 11°. (figure 4)