An oar is an implement used for water -borne propulsion. Oars have a flat blade at one end. Rowers and canoeists (not kayakers) grasp the oar at the other end.
The difference between oars and paddles are that oars only have oneblade, and are used exclusively for rowing, whereas paddles can have either one or two blade and are not rowed. Oars for rowing are generally connected to the vessel by means of rowlocks or tholes which transmit the applied force to the boat. In this system (known as a second class lever) the water is the fulcrum. Oars for canoeing are held by the canoeist.
Rowers generally face the stern of the vessel, reach towards the stern, and insert the blade of their oar in the water. As they lean back, towards the vessel's bow, the blade of their oars sweeps the water towards the stern, providing forward thrust – see lever.
For thousands of years vessels were powered either by sails, or the mechanical work of rowers, or paddlers.
