Apparatus, systems and methods in accordance with the present invention are related to rotary cutting tools and rulers. In one illustrative embodiment of a system in accordance with the present invention, a ruler for use with a rotary cutting tool has a guide ridge formed as a wall along a cutting edge of the ruler. A hand held rotary cutting tool has a groove in a cutting portion thereof that corresponds to the guide ridge and resides thereon during cutting. The rotary blade of the hand held rotary cutter is maintained in a position adjacent to the cutting edge of the ruler as the cutter is advanced long the ruler cutting edge by the interaction of the groove and the guide ridge. The cutter may include blade guard locking features and a blade depth control for additional safety and control during use.