In rowing, oars are used to propel the boat. Oars differ from paddles in that they use a fixed fulcrum to transfer power from the handle to the blade, rather than using the athlete's shoulders or hands as the pivot-point as in canoeing and kayaking. Typical Sculling oars are around 284cm - 290cm in length, and rowing oars 370cm - 376cm long. The shaft of the oar ends with one flat end about 50cm long and 25cm wide, called the blade. The part of the oar the oarsman holds while rowing is called the Handle#Noun. While rowing, the oars are supported by metal frames attached to the side of the boat called riggers.
The parts of an oar are (labelled from outside first): blade, loom, 2/3rds of the way up is the collar (consisting of wearplate and sleeve) and button, and at the very end the handle and grip.
An oar is often referred to as a "blade" in the case of sweep oar rowing and as a "scull" in the case of sculling. A sculling oar is shorter and has a smaller blade area than the equivalent sweep oar.
There are hundreds of different variations of oars, but "Macon" or "Cleaver" blades of carbon-fiber are the most common in modern sport rowing. Classic oars were made out of wood, but since the use of synthetic materials, the weight of an oar has come down from over 7 kg, to less than 2.5 kg.
The blade shapes are commonly "macons," "spoons," or "tulips" which are used for novice boats, and "cleavers" or "hatchets" which are used for racing boats. A macon oar has an elliptical shape and has a ridgeline running down the center of the blade face, around which the blade face is symmetrical. The blade is squared off at the end. Due to the blade face symmetry, macon blades are ambidextrous and can be rowed either on the port or the starboard side of the boat, although in most cases, aesthetic issues concerning the decorative paint on the blade faces may dictate an oar as belonging to one side of the boat or the other.
A hatchet blade's face is somewhat rectangular and looks like a hatchet, hence the name. The shaft of a hatchet blade connects to the hatchet offset to the top edge of the blade. The shape of the face and the offset connection is designed to maximize the surface area of the blade in contact with the water during the rowing stroke, while also minimizing excess material that would not contribute to driving the boat through the water. A hatchet blade is not ambidextrous.
Prior to the development of the macon blade a longer, thinner shape was used, now referred to as "pencils" and occasionally used in training for technique. The development from pencil to hatchet, via the macon, is therefore a progression from long, thin blades to shorter, wider ones. In each case there has been a reduction in the area of the blade that actually moves the wrong way through the water: in practice a point of the blade remains stationary relative to the water, with the portion outboard of that point providing drive, and the area inboard of it providing drag. Shorter, wider blades place this pivot point closer to the blade's loom, reducing the area dragging in the water.