The sill is the single most important structural area of the monocoque body and also one of the most common rust locations, particularly on the lower outer face, which is exposed to stone chips, road salt, kerbing damage, and standing water from blocked drain holes. The outer sill panel traps moisture between itself and the inner sill, and once corrosion establishes itself in this enclosed space it progresses rapidly from the inside out, so by the time it is visible on the outer surface significant structural damage has usually occurred within the box section. Sill replacement is one of the most common and costly body repair tasks, typically involving cutting out the corroded outer sill, repairing or replacing the inner sill and jacking point reinforcements, and welding in new panels.
Protection & Styles
Stainless oversills fit over the outer sill panel between the front and rear wheelarches, serving both a protective and visual purpose. On a car that has had new outer sills fitted as part of a restoration, they protect the fresh metalwork from the conditions that caused the original corrosion, and on a car in otherwise good condition they cover minor surface blemishes on the lower sill face while providing ongoing protection, making them a sound investment particularly after a sill repair where the new metalwork deserves preservation. They are available in several fixing styles, from an unobtrusive narrow stainless attachment strip to a more robust alloy finisher with a coloured plastic insert in black, blue, green, red, silver, or white, allowing the detail to coordinate with the car's colour scheme. The polished stainless finish also provides an attractive bright accent along the lower body line that complements chrome bumpers and door handles.
The six-piece original equipment side moulding set is a related but separate item, as the oversills sit lower on the body, covering the sill face below the moulding line.