Read the following article and answer the question.

This allows the side frame to pivot so the wheels stay in good contact with the rail over any rough track work . Granted they do not move much and should not if the track has been layed correctly . The bad news is this is the side I need to add the extra pick up to . I have read a number of articles where the extra pickups are always added to the bottom of the truck and rub on the backside of the wheels .

What am I working on that I may have to add an extra pick up ?
I am working on a truck and may need to install more parts .