The Cessna strut braced wings bolt to the aft spar carrythrough with an eccentric "cam" in the joint. This cam is punched with a mark so the person adjusting knows which direction they are being turned. Their intended function is to raise or lower the aft spar of each wing independently, relative to the fuselage, when turned with the wing attachment bolt loose. However, while moving the aft spar up or down by turning the cam, the biproduct motion can be to also move the aft spar a tiny amount closer or farther from the fuselage attachment (it depends upon how far, and which direction the cams are turned). Turning the cam(s) so that the rear spar is brought closer to the fuselage has the unintended effect of very slightly sweeping that wing back. If the spar is pushed a tiny amount away from the fuselage will sweep the wing a tiny amount forward. As long as both wings are swept either forward or aft, and the incidence is adjusted so that the plane flies level, all is well. It's when one wing is swept forward, and the other swept aft, the axis of the wings is not square to the axis of the fuselage. Thus the plane does not want to fly straight, but the reason is not apparent, 'cause it's not in the tail.
This was all explained to me some time ago by a Cessna rep when I inquired as to why two otherwise identical C150s had differing performance (we tested in formation). One was a little faster, the other would fly just a little more slowly at low speed. The Cessna rep explained that the fast one had the wings swept aft, and the slow one wings forward. When we removed the fairings, and looked at the cams, this made sense. We never adjusted the cams on either plane to experiment more, as they otherwise flew fine. Certainly I have check flown other Cessnas where wing cam adjustment, and reflying was a part of the post maintenance procedure. This is described in 4.7 of the 172 Service Manual, "Adjustment (Correcting Wing Heavy Condition).