The aluminum bolts may be used two times. Therefore, the bolts must be marked with an made by a chisel after they have been used the first time.
WARNING: This page is about a different car, the 2024 Audi A6 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
To prevent damaging the bolts when marking them, do not clamp them in a vise. Insert the bolt in a 14 mm socket with a 1 /2 drive, which is inserted in to the vise, as shown.
Bolts marked with an "X" may not be used again.