There was an interesting post by Chris Schwarz on the woodworking magazine blog titled "Tapered Sawblades: That's Not a Defect, it's a Feature" about how this helps not overshoot the back of a cut. Essentially saws that when you hold them level cut deeper at the front so you hit the line closest to you first and then you can finish up the back side. Apparently Mike Wenzloff's dovetail saw is like this. It's worth a read.
I have found the mirror very helpful when cutting dovetails, although you need to get the position just right.
I have used the mirrors with great success since I read about it some where. Nice tip to pass on to fellow Neanders. Happy holidays. John
Harry and all
A mirror is not necessary. Waste of time.
Rule #1: Have the face (outside) of the board facing you as you cut.
Rule#2: Make sure that you cut to the baseline on the face. If you go over this line it will show in the final result.
Rule #3: If you go slightly over the line on the reverse side it does not matter - it will not be seen!
My most recent set of dovetails (yesterday). A presentation box in Tasmanian Blackwood ...
The box contains two chip carving knives.
Regards from Perth
Derek