Power source
(12) Power source means an engine or motor. (13) Reel-type mower means a lawn mower which cuts grass by rotating one or more helically formed blades about a horizontal axis to provide a shearing action with a stationary cutter bar or bed knife. (14) Rotary mower means a power lawn mower in which one or more cutting blades rotate in essentially a horizontal plane about at least one vertical axis. (15) Separate means to cause to have any apparent relative displacement induced by external forces. (16) Shield means a part or an assembly which restricts access to a hazardous area. For the purposes of this part 1205, the blade housing is considered a shield. (17) Stress means a force acting across a unit area in a solid material in resisting separation, compacting, or sliding that tends to be induced by external forces. (18) Top of the mower's handles means the uppermost portion(s) of the handle that would be gripped by an operator in the normal operating position. (19) Walk-behind power lawn mower means a grass cutting machine either pushed or self-propelled, with a minimum cutting width of 12 in (305 mm) that employs an engine or a motor as a power source and is normally controlled by an operator walking behind the mower.