When planning the installation site, you need to allow sufficient clearance around the rack (see Figure 1):
Figure 1: Chassis Dimensions and Clearance Requirements

The router has two adjustable center-mounting brackets that are initially attached to the mounting holes closest to the rear of the chassis. You can move the pair of adjustable center-mounting brakcets to one of 11 positions on the side of the chassis. The mounting holes for connecting the mounting brackets to the chassis are spaced 0.984 in. (25 mm) apart.
For instructions about installing the mounting hardware, see Installing the M320 Mounting Hardware for a Four-Post Rack or Cabinet.
The chassis height of 34.80 in. (88.4 cm) is approximately 20 U. A U is the standard rack unit defined in Cabinets, Racks, Panels, and Associated Equipment (document number EIA-310-D) published by the Electronics Industry Association. You can stack two M320 routers in a rack that has at least 40 U (70 in. or 1.78 m) of usable vertical space.
The rack must be strong enough to support the weight of the fully configured router, up to 439 lb (199.6 kg). If you stack two fully configured routers in one rack, it must be capable of supporting about 878 lb (399.1 kg).
Figure 2: Typical Open-Frame Rack
