A truck's tie-rod helps steer the vehicle. It is part of the mechanism that causes the truck's tires to turn while steering. The rod itself is a bar with a connector on each end. It is position near the wheel of the vehicle, making it susceptible to erosion and damage, which is why they should be checked regularly. If a tie-rod goes out, it can damage your tires over time, it can cause your truck to veer in either direction when the steering wheel is not gripped firmly and it can knock steering out of alignment. See a truck repair specialist to have your tie-rods checked regularly.