The Shear Line is the imaginary line which evenly divides the formation into two halves, and along which exactly half of the dancers have been shifted 50% relative to the other half of the dancers. Assuming that you are Squared off to the walls and that the caller is at the North or South end of the hall, the Shear Line is either a North-South dividing line (henceforth called a Head Shear since it bisects the square through the Heads initial starting position), or an East-West dividing line (henceforth called a Side Shear since it bisects the square through the Sides initial starting position). Note that the Shear Line always passes through the very Center of the set. EN: 40

The Shift Direction is the direction along the Shear Line in which the dancers have been shifted. The Shift Direction is either Clockwise (CW) or Counter-Clockwise (CCW). Note that "Right" or "Left" or "Up" or "Down" would be insufficient information, since exactly half the dancers would be shifted in one direction (e.g., "Right") while their opposite dancers would be shifted in the opposite direction (e.g., "Left"). Right-Left fails to clarify which half of the square is shifted in which direction (i.e., is the top half shifted Right, or is the bottom half shifted Right?). CW and CCW, on the other hand, indicate the Shift Direction of both halves of the square at the same time. To determine whether the Shift Direction is CW or CCW, imagine grabbing the dancers on one side of the Shear Line with one hand and grabbing the dancers on the other side of the Shear Line with your other hand, almost like holding a steering wheel. Now, imagine simultaneously moving both halves of the square along the Shear Line in the direction of the offset, one hand in one direction and the other hand in the opposite direction. If you turn the "steering wheel" to the right, the Shift Direction is Clockwise (CW); if you turn the "steering wheel" to the Left, the Shift Direction is Counter-Clockwise (CCW). EN: 50