Carpenters hammer it harder. Carpenters do it indoors. Carpet Layers do it on the floor. Cheerleaders do it with more enthusiasm. Chem E.'s do it in packed beds.
Chemists do it periodically on table Chemists like to experiment.
Chess players do it in their minds. Chess players do it with royalty. Chess players check their mates. Chiropractors do it by manipulation. Choir boys do it unaccompanied.