The base plate on circular saws has a cutting guide with markings for 0 and 45 degrees. If you are cutting an intermediate angle such as 22.5 degrees where do you line up the cutting guide?

Dear Paul,
22.5 degrees of angle is exactly 1/2 of a 45 degree angle. This is difficult to set on a circular saw. Usually I use a engineers adjustable square to make templates and set the plate to blade angle with them.
Len