The quality of this stage determines whether the final finish looks right and whether it lasts.
Body filler is a two-part polyester product that fills low spots and dents. It is applied over clean, properly prepared metal and shaped by sanding. Filler is not a substitute for straightening — deep dents filled rather than pulled will crack and shrink. Glaze and putty are thinner products for pinholes and shallow imperfections.
Panel adhesives and rivets replace welding on modern vehicles. High-strength steels used in current body structures lose their properties when welded, so manufacturers specify adhesive bonding and self-piercing rivets instead. Following the manufacturer's repair procedure is not optional on these vehicles.
Preparation materials — sandpaper, sanding blocks, prep solvent, tack rags, masking tape and film — determine whether the paint bonds. Contamination left under a coating shows up later as lifting, fisheyes or peeling. Block sanding with the right block and grit progression is what makes a panel straight.
Specialty repair materials cover plastic repair, aluminium repair and structural adhesives. Plastic bumpers and panels need a specific repair system; welding them with the wrong method melts and ruins them.
