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Got a rack with weird/large holes.

I have put a piece of plywood agains the wall to hold a server rack. This guy: https://www.tripplite.com/smartrack-10u-low-profile-switch-depth-wall-mount-rack-enclosure-cabinet-clear-acrylic-window-hinged-back~SRW10USG

It's about 50 lbs, supports 200 lbs.

I have the plywood secured as so: (left stud is at an angle) enter image description here

The holes in the server rack are rather large. What fastener should I use for it? The smallest hole measures 3/8" across.

enter image description here

Edit: This stock picture of the entire back from the website linked might clarify the mounting hole issue for some: enter image description here

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  • Detailed wall mounting instructions are in the manual, which is on the page that you linked in the question.
    – jay613
    Commented Dec 11, 2021 at 0:50
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    Also it looks like you had the outlet and that ceiling access hole created expressly for this cabinet. Why then didn't you just open up the wall, beef up the framing, and finish it with plywood instead of wallboard?
    – jay613
    Commented Dec 11, 2021 at 0:53
  • Not sure I follow, it is plywood and I have it attached to two studs. Also, the manual is vague on install. There is no details on what fasteners to use or what material you are securing the rack to.
    – amrog
    Commented Dec 11, 2021 at 1:46
  • If it's built to order for putting a rack in (as @jay613 observed) then It's relatively easy (at build time) to install blocking between the framing so your rack can mount to wood framing (where longer lags would have something to grab) behind the face of the wall. At the same time, if you still want a plywood face to mount to, you can skip the drywall and attach the plywood directly to the framing and blocking, rather than mounting the plywood on top of the drywall. No need to redo it, but it's a valid observation given that other customizations for being a "server closet" have been done.
    – Ecnerwal
    Commented Dec 11, 2021 at 2:05
  • @Ecnerwal said what I meant. :). Add blocking to align with holes and move or note wire and pipe locations so you can use your 4 inch screws safely and effectively. Don't need wall at all, the metal rear door is adequate mounted directly to correctly placed studs. Bottom of page 5 says use four M8, M10, 5/16” or 3/8” bolts with fender washers spaced 16 inches apart horizontally. That's quite specific. And I agree that if you don't do this but mount only to ply you should do exactly what's in the answer: Use 1/4 x 1-1/4 screws, 6 along the top and 4 long the bottom.
    – jay613
    Commented Dec 11, 2021 at 15:29

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1/4 x 1-1/4 or 5/16 x 1-1/4 or 3/8 x 1-1/4 lag bolts, and washers. Perhaps even fender washers, if you like. Do feel free to use more than 4 total, especially in the top holes, since you are screwing into ply, not trying to hit framing. Should be easy to use 6 (doubling only the tops) or 8 (if you also double up the bottoms) making use of the outermost and innermost holes.

More length won't do a thing for you with (evidently you don't say, but presumably) 3/4" plywood. The extra 1/2" accounts for washer, backpanel, and the pointy end of the lag bolt that doesn't hold much.

By the way, the fasteners you used for the plywood are risky in the extreme. Electrical and plumbing code assumes that you won't penetrate framing more than 1-1/4" when instructing where cable/pipe protection plates are needed. If you happened to hit a cable when putting one of those in, the fault would be entirely on you. Longer is NOT always better with lag bolts and screws into framing, especially if you don't personally know exactly where the wiring/plumbing isn't. With 3/4 ply and 1/2" sheetrock, your fasteners should not have been more than 2-1/2" long (which would also be plenty.) Given that you counterbored the heads of the lag bolts in, 2" for those.

4 2-1/2" screws (2 at top, two at bottom, about 1 to 1-1/2" from the edge) would improve your structural attachment, however. Especially the top ones, if you only do two instead of 4. Leverage matters, and the top screws want to be as far up as possible without breaking out of the edge of the plywood so they have the most leverage against the loaded rack trying to peel that plywood off the wall. The same logic applies for doubling up the top mounting bolts for the rack itself.

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  • Thanks @Ecnerwal. I was thinking I needed 4" lags before I realized that I needed to countersink the lag bolts so the rack would fit against the plywood. I do know where the electrical and plumbing is located. Nothing is in the wall space in question.
    – amrog
    Commented Dec 11, 2021 at 1:50
  • You recommended 4x 2 1/2 inch screws (lag bolts??) on the top and bottom to improve structural integrity. Could I use 3" deck screws instead?
    – amrog
    Commented Dec 11, 2021 at 1:53
  • So long as you are 110% certain there's no wiring or plumbing to hit there, yes.
    – Ecnerwal
    Commented Dec 11, 2021 at 1:55
  • Did I mess up the structural integrity of the plywood by countersinking the lag bolts?
    – amrog
    Commented Dec 11, 2021 at 2:06
  • For the whole sheet - no. For the ability of the part of the sheet the lags are grabbing to be anywhere near as strong as the lags' hold into the framing, quite possibly. How thick IS the plywood, and how deep is the counterbore? If there's a couple of inches of plywood above and below the rack, you could remove them and put them where they won't interfere with the rack, above and below it, not counterbored.
    – Ecnerwal
    Commented Dec 11, 2021 at 2:09

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