Bump-steer is essentially a change in toe-in during suspension travel. To properly perform this alignment, the technician will put your vehicle on an alignment rack so the front wheels are on movable tables. He will then likely hook a come-along to the crossmember and one to the floor that will allow him to pull the vehicle throughout its suspension travel to measure the change in toe (bump-steer). He will then re-arrange the rod ends vertical positioning to minimize the problem.
In many cases, a subtle lowering of a car will not be enough to induce bump-steer, however, severe lowering, or the use of camber-caster plates will often cause the problem. By changing the angle of the tie rod assembly, done by extending or lowering the pin height, you can decrease your bump-steer to very small levels (less than factory).
Installation instructions can be found below under "Attachments".