Rowlock – In the boating world, a rowlock is the U-shaped device that holds an oar in place and acts as a fulcrum during rowing. But this website is based in the construction world. Around here, a rowlock refers to a classification of laid brick.
It defines how the exposed face of the brick is oriented relative to the face of the finished wall.
As the picture indicates, a rowlock is a run of bricks laid on the long narrow side with the short end of the brick exposed. Alternate brick orientations include stretcher, header, soldier, sailor, and shiner.