The H967 rack (officially the H967 Short Heavy Duty Cabinet Frame) was the short version of the H950 cabinet, DEC's standard 19" wide rack (an industry-wide standard width for rack-mounted gear), used with the PDP-8, PDP-11, etc.
The H967 included add-ons such as the rear door, side panels, etc.
It was 4' (49.63") tall, and provided 42" of mounting space. The mounting space in the H967 was divided into 4 10-1/2" units, each of which could be further sub-divided into two 5-1/4" spaces. Most DEC gear (e.g. BA11 mounting boxes) was designed to fit in spaces of these sizes.