Lower bars at birdcage?

Can anyone explain what happens when you move the lower bars on the birdcage? How do you know what position to start in when the chassis manuf doesnt give one? Just not fimular with the lower bars at the birdcage.

Standard starting position on the birdcage from almost all manufacturers is 4.5" from the center of the axle tube. This is true of the upper bars also.
In general, adjustments made at the birdcage have the opposite affect of adjustments made on the frame side of that bar. For example, lowering the bottom right bar on the frame tends to tighten entry while lowering the bottom right bar on the birdcage tends to free entry.
Also in general, adjustments made at the birdcage tend to have a more drastic affect on handling.

Thanks Matt. In addition to what you said, what would be the result of moving both LR upper and lower bars down or up the same amount?