On Tue, 15 Nov 2005 17:06:56 -0600, Chris Friesen
wrote:

There are marking gauges with knives or sharp wheels rather than pins
for this exact reason.

"Marking" gauges traditionally use pins. The ones with knife blades are
called "cutting" gauges. For marking out dovetails they do indeed cut
a better line. However they're not recommended for marking mortices, as
they tend to self-steer when following along the grain.

A good compromise is a gauge with a pin, but to sharpen it on two sides
as a narrow knife blade.