A Concept2 oarlock has a built-in pitch: the face against which the sleeve of the oat shaft is resting during the drive is pitched by 4 degrees. This assumes the oarlock pin is vertical.
This pitch can be adjusted using the blue bushings that connect the oarlock with the metal pin. Bushings come in variants and are labeled with numbers that are opposite each other: 4/4, 5/3, or 6/2.
A: By default, 4/4 is used and it results in the standard 4 degree pitch.
B: To increase the pitch to 6 degrees, one would use bushings that are labeled 6/2 and insert them such that the 6 on the top is adjacent to the gate and at the bottom the other way round. This tilts the entire oarlock mechanism such that pitch is now 6 degrees.
C: Conversely, to reduce pitch to 2 degrees, the same bushings would be used but inserted 180 degrees rotated. Now 2 is adjacent to the gate. Again, the oarlock is tilted such that the resulting pitch is 2 degrees.
Smaller changes are possible. The 4/4 bushings in the picture above can be also used to create 5 and 3 degree pitch.