The rear end section covers the side of the base of a windscreen window pillar.

A rear end section (49) for reinforcing the window pillar extends tilted upward and toward the rear from the top of said rear section (47).

The present invention can be used to weld the window post of one side of the body shell of a motor vehicle.

It makes use primarily of the window post (3) liner, which is situated behind the upper center pillar reinforcement (2).

The system allows welding of a hollow tube (2) on the window post (3) on one side of the body shell of a motor vehicle without reflecting the welding efforts on the welding system's support.