IBM ThinkPad T21 Hardware Maintenance Manual page 112

Removing and replacing a FRU
When installing: Make sure the followings:
v a -parts of the insulation do not come off.
v b -part ( b' s are only for T23 series) is not turned
over.
v Holes in the guide rail and in the aluminium sheet are
aligned, and the aluminium sheet does not protrude in
the c -parts. The protruding parts of the sheet can
cause electrical short.
c
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ThinkPad T20, T21, T22, T23 (MT 2647/2648)
a
a
b'
b
a
b'