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v They are harder to tighten.
v They should be used only once.
Do the following when you service this machine:
v Keep the screw kit (for reference the P/N, see
“Miscellaneous parts” on page 96) in your tool bag.
v Always use new screws.
v Use a torque screwdriver if you have one.
Tighten screws as follows:
v Plastic to plastic
Turn an additional 90 degrees after the screw head
touches the surface of the plastic part:
v Logic card to plastic
Turn an additional 180 degrees after the screw head
touches the surface of the logic card:
v Torque driver
If you have a torque driver, refer to the “Torque” column
for each step.
v Make sure you use the correct screw. If you have a
torque screwdriver, tighten all screws firmly to the torque
shown in the table. Never use a screw that you
removed. Use a new one. Make sure the screws are
tightened firmly.
Retaining serial numbers
This section includes the following descriptions:
v “Restoring the serial number of the system unit” on
page 49
v “Retaining the UUID” on page 49
FRU replacement notices
48 ThinkPad A21e