For quick, accurate marking of dovetails, a dovetail marker is the best tool available. 
With riding ledges on both sides, these 2" x 2" markers can be flipped over to mark both slopes of the dovetail. They are designed so that the entire ledge is riding on the reference face, even when marking edge dovetails. The relieved corners at the join of the body and the riding ledges ensure perfect seating even on saw whiskers. Made from anodized aluminum, these markers are light, durable, and never soil your work.
Available as a set in the traditional ratios of 1:6 for softwood and 1:8 for hardwood. The 14° marker is designed to approximate a 1:4 ratio, for those who prefer this angle when working in thinner stock, as it not only provides stronger material interlock than traditional ratio angles but produces a slightly exaggerated dovetail joint that many find attractive.