What are "knock outs" in reference to alignments? on 1997 Chevrolet 1500 Pickup

I've been told in order to get an alignments, "knock outs" have to be removed and they charge an addition $50.00 to do this work. Never heard of such a thing. What are "knock outs"?

by in Arvada, CO on October 11, 2012
Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
2 answers 1 comment
ANSWER by , October 11, 2012
knockouts are metal or plastic tabs that the factory puts in trucks so that it holds the alignment that was set at the factory. when you get your first alignment done at a shop they usually have to remove these tabs hence why they are called knock outs. because they have to knock them out to adjust the camber and caster.
COMMENT by , October 12, 2012
Once an alignment has been done, do they replace the tabs? Can an alignment be done on only one side of a vehicle? Apparently one side of the vehicle has had "alignment" work on it so the "knock out" is gone. I'm just trying to see if information the mechanic is true as I find it hard to trust them when it doesn't make sense.
ANSWER by , October 12, 2012
a little high in price but it is hat it is. are you happy with the way the car drives