Panasonic Toughbook CF-U1A1B1G2M Reference Manual page 36

Battery Power
9
Pressing and holding the battery cover, slide the latch to
fix.
10
Attach the hand strap back to the original form.
Take the step
CAUTION
Make sure the latch is securely locked, otherwise the battery pack may fall when you carry the computer.
2
(A to C) in the reverse order.
36
A A