A putt ruler is a device that separates the skills of straight-line putting from reading the green. The putt ruler may be affixed to the golf green and may be rotated to align with the identified target line. Through placement of two golf balls atop the putt ruler, a golfer may produce a putt that follows a straight line, when the stroke used may not have produced a straight-line putt on a single golf ball. The golfer may then evaluate the chosen target line in relation to the resultant putt and evaluate the speed of the putt as the ball travels along the playing surface.