Oarlocks or locks are a more common form of attachment for oars as they allow the rower to "feather" the oar back and forth as they row making it easier on the person using the oars to continue downstream. Oarlocks look like a pin topped with a U-shaped metal flange. The oars slide into the gap between the U-shaped metal pieces and can be held in place with a plastic stopper called an oarlock.