The H960 rack and H961 rack (officially the H960 cabinet and H961 cabinet), built around the H950 frame, were DEC's standard 19" wide rack (an industry-wide standard width for rack-mounted gear), used with the PDP-8, PDP-11, etc.
The H950 is the bare rack; the H960 included add-ons such as the rear door, side panels, etc. The H961 was intended mostly for expansions, and did not include the side panels, but did include a pair of filler strips (to go between the racks).
It was 6' (71.75") tall, and provided 63" of mounting space; DEC also came out with some shorter 19" racks (e.g. the H967 rack). The mounting space in the H960 was divided into 6 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.
Under the main part of the cabinet, and also at the tips of the 'stabilizer feet' (DEC's official name for the extension feet on the front a cabinet, to keep it from tipping over when units are slid out), there are 'levelers' (again, DEC's official term) - threaded rods with a metal cup holding a circular rubber pad. These are often damaged or lost, but replacements are available.
The small ones at the tips of the extension feet are 5/16"-18 thread, and a suitable replacment part is the Vlier FSE302S. They fit OK, with two caveats:
- The round foot part is a significantly larger diameter than the DEC originals, but they do fit OK on neighbouring extension feet (i.e. on a pair of H960's, both with extension feet).
- The threaded shaft is somewhat longer than the originals, so even when wound fully up, there isn't a lot of room between the foot and the floor.
The larger one under the cabinet are 1/2"-13 thread; Vlier makes suitable replacements for them, too - FSE306S. Like the smaller ones for the extensions, the pad on the bottom is somewhat wider than on the DEC originals, but they still work fine.