Monster MT-SB21 User Manual page 6

Installation - Free Standing
This soundbar can sit free-standing on a surface, or it can be mounted to a wall.
Note: the subwoofer cannot be wall mounted.
Free standing
6 | PRODUCT OVERVIEW
Place on a secure, flat surface. Make sure the soundbar
is standing on its rubber pads (on the left and right sides
of the soundbar) and no other area of the bottom of the
soundbar is touching the surface.