This method is fine for new chain, and it stinks for chain with moderate to heavy wear. (The Pferd/Stihl does it the same way as the old .025 gauge, it rests a rail on the tooth you are cutting and the next tooth, and has a flat file .025 lower than the bottoms of those rails.)
How many times have y'all said, "Well, I did what the depth gauge says, but these rakers need another lick... still making sawdust, maybe a few more..."
There's a good reason for that. (The reason is that .025" makes a 5.7° angle with the wood on a new tooth and about a 2° angle with the wood on a used up tooth.) The answer to the problem is progressive raker adjustment. The simple method is the old Fileoplate gauges (FOP is gone but Husky still makes them). This chain has most of the tooth left and the rakers are adjusted to a 6° AoA- you can see the Husky gauge almost agrees with this height. (This chain cuts like a light saber too.)
A significantly better but slower method is to directly measure the angle between the tooth and the raker (done with a pair of calipers and some math, or with an angle finder.)
Here's that same raker with an old 0.025 flat gauge on it. This style gauge says that 6° is WAY too low!- and this chain has most of its tooth length left! (Factory grind is usually 5.7°.) If this was an old worn out chain the difference would be even more.
I think we're not supposed to link other forums but I am going to anyway, because everyone who uses a chainsaw more than a little should know how great this idea is. (And not great as in, "that sounds great", but great as in, "all my worn out old chains cut like new ones".)
If the link gets automoderated out, Google for
"Are FOP really progressive depth raker generators?"
BobL's classic progressive raker adjustment thread