Siemens SIPART PS2 6DR50xx Manual page 30

Design and Functional Principle
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30
NOTE
To prevent premature wearing of the fixture by the self-tapping screw
(1.1) next to the display, the following method of mounting the module
cover (1) has proven effective.
1. Turn the screws counterclockwise until you feel them snap into the
thread.
2. Tighten both screws carefully in clockwise direction.
SIPART PS2 Manual
A5E00074631--06