The example of rowing a boat is a good example of a first class lever. In a first class lever, you have the fulcrum, which is the fixed point against which the lever works, between the effort force and the resultant force. The effort force is the force you are putting into the machine, while the resultant force is the force the machine is turning out. The effort force would be you pulling on the oar, the fulcrum would be the oarlock, and the resultant force would be the paddle end of the oar pushing against the water. A second class lever has the fulcrum at the end of the lever, the resultant force in the middle, and the effort force on the end closest to you. A wheelbarrow is a good example of a second class lever. A third class lever has the fulcrum closest to you, while the effort force is in the middle and the resultant force is on the end farthest from you. A paint brush applying paint is a good example of a third class lever.