Ubiquiti PowerBeam M5 PBE-M5-620 Quick Start Manual page 7

5. Attach two Hex Head Bolts, two Lock Washers, and two Flat
Washers to the bottom of the Mounting Bracket. Ensure that
there is a gap of 8 mm between each Flat Washer and the
Mounting Bracket.
Note:
installed between the Hex Head Bolt and Flat Washer.
Flat Washer
Lock Washer
Hex Head Bolt
Ensure that each Lock Washer is always
8 mm