Dave Pelz uses the phrase, PILS (pure in-line stroke). Most amateurs use the term "pendulum". In order to have good distance control, it is essential to allow the swing weight to do its job by relaxing your arms so the putter swings like a pendulum. The distance the ball travels is based on how far you take the putter back not how firm or soft you swing the putter. Feel the weight of the putterhead.