Squeezebox Boom Mounting Bracket
From SqueezeboxWiki
A wall and under shelf/counter mounting bracket is available as an accessory to Squeezebox Boom.
The brackets and included hardware allow you to mount a Squeezebox Boom to the wall (drywall, wood, cement) or under cabinet (through hole or solid wood shelving).
Nearly-final drafts of the instructions that will be included are available here:
Squeezebox Boom Mounting Instructions
Squeezebox Boom Mounting Template
technical note: the four screws at the bottom of the Boom are metric M2.5