Digital Data Communications LEVEL ONE FCS-4400 - Manual (Page 13)

Hook up the safety buckle, and screw the two screws to fix the power box.
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CAS-4000B ceiling mount kit
Fixed the iron tube to the cover of power box.
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CAS-4000C corner mount kit
Combine two brackets, and use the spanner to fix the screw.
Turn the screw to tighten the brackets and power box.