Marking knives are simple tools, but crucial to fine craftsmanship. A good one will cut wood fibers cleanly, leaving a crisp line that's deep enough to anchor a chisel.  It must fit into tight spaces and be easy to hold using a pencil-style grip. Users of marking knives, such as Steve Latta, often choose a knife based on the type of work they do. With this in mind, Latta sampled more than a dozen knives, using them to mark out dovetails, trace a hinge, mark for a banding, and trace the boundaries of an inlay mortise. The knives ranged widely in price, up to about $45. Yet his favorite costs less than $3.

From Fine Woodworking #198