There are two basic types of gauges used with crosscut saws.
The metal thickness gauge is rarely used and may be used to determine the thickness of the metal the saw is made of. I obtained several in an attempt to verify the amount of gauge variation between the teeth and the back of a saw. I have included raker depth gauges in this group.
The Spider gauges are used to determine the amount of set that is put on the saw's teeth when it is being sharpened/tuned.