52 17... Removing and installing outer upper rail cover

Move seat backwards and upwards.

Unclip cover (1) towards front.

Fig 1: Removing Outer Upper Rail Cover

Courtesy of BMW OF NORTH AMERICA, INC.

Driver's seat only: 

Feed cover out of seat mechanism:

1. upwards,
2. slide towards rear

Feed out cover.

Fig 2: Removing Cover From Seat Mechanism

Courtesy of BMW OF NORTH AMERICA, INC.