Introduction: Secret HVAC Vent Vault

About: Welcome to my Instructables channel where I'll share my wacky and unique creations that hopefully others find useful, or better yet, inspire an evolution of even better ideas!

Hiding things in plain sight is sneaky, fun, and most importantly effective! (Here's another example.)

This Instructable is an entry in the "Secret Compartment Challenge". Please vote if you like it.

I'll show you how to easily and cheaply add a secure hiding place in your home, small or large, for storing your valuables.

PROJECT SUMMARY: A modified vent cover that hides a secret opening in your wall. It uses magnets to attach for quick and easy access to your new in-home vault.

BONUS: For renters too, because not even the landlord will notice your empty vault when you leave.


  1. Fixed Vent (Many sizes to choose from) or
  2. Adjustable Vent (My Choice)
  3. Magnets (10mm X 5mm)
  4. 2-Part Putty Epoxy (Marine or Metal)
  5. 1"X2" Wood
  6. Construction Adhesive
  7. Drywall or Other Countersink Screws (Recommend Self-Tapping)
  8. Tape


  1. Drywall Saw
  2. Wood Saw
  3. Wire Cutters (Or other tool to cut the screws to length)
  4. Stud Finder (Optional)
  5. Level (Optional)
  6. Carpenter's Square (Optional)

Step 1: Determine the Location

Most central air vents are located near the ceiling. So to be inconspicuous, you want to maintain that position and the same vertical distance as the actual vents. A vent right in the middle of the wall, while easy to access, also looks out of place.


  • Locate near an existing vent
  • Locate mid-way between floor and ceiling
  • Locate on exterior walls or where insulation will be present inside the wall cavity
  • Locate on any pony walls or walls where a cabinet is on the opposite side (these are locations that obviously couldn't have duct work inside the wall)

TIP: If you prefer a floor level location for your vault, choose an extra wide vent, as these are sometimes used as returns to a central air system, and thus will not look out of place at floor level.

Step 2: Locate Studs

Studs are the vertical wood pieces inside your walls. I've done this enough that I can tell by sound, but for most people a stud finder is recommended. You want to position your vault roughly mid-way between two studs to maximize the space you'll have access to. (Or if you'll be creating a shelf or other type of enclosed space you may want to locate it right next to a stud to have a vertical foundation to build from.)

TIP: If the location you choose has an electrical outlet near it, you can use the outlet as a reference for where the studs are. Generally, outlets are mounted to the sides of studs (See image above). So a stud will either be located to the left or right of the outlet. If you pull the outlet cover off you may be able to see the stud.

CAUTION: If using a small nail to find the studs, don't do this directly to the left or right of the outlet. You may hit the exposed wires of the outlet. Go a few inches above or below the outlet to reduce the risk of hitting the wires.

Step 3: Test Hole

Drill a small hole, but large enough to shine a light and see into, where you will be locating your vault.


  • No insulation is present
  • No duct work is present
  • No water supply or drain lines are present

Step 4: Rough Out the Opening

Again, here are the fixed vents or the adjustable style. Both of these are probably the most common style out there, but if yours are different you'll need to find the exact ones (or color if yours are not white).

  1. Step 1 - Easy for us guys - Toss the instructions in the trash. Do NOT cut the hole per the instructions if they came with the vent.
  2. For the adjustable style, refer to the image above for where you want to measure the Width and Height of the opening (Green arrows good. Red arrows bad.)
  3. For fixed vents, a good rule of thumb is to cut the opening just slightly larger than where the louvers are. This gives you plenty of space while maintaining the proper "look".

NOTE1: Use a level to ensure the opening is level and plumb.

NOTE2: Test fit the adjustable vent to make sure the opening is not too small before starting the next step.

Step 5: Framing the Opening

  1. Cut pieces of 1"X2" wood to frame the inside of the opening:
    • See image above
    • Long side of the 1"X2" will be in contact with the backside of the drywall
    • Ensure the wood is flush to the cut edges of the drywall
  2. Use the construction adhesive to secure the wood to the inside of the drywall one piece at a time (Just the glue, no fasteners yet)
  3. Use tape if needed to hold the wood in place while the glue dries
  4. Allow the glue to dry overnight

NOTE1: Don't miter the joints. We'll be installing screws in the corners and you don't want the screw to penetrate right at the mitered edges. Simple butt joints are best here.

NOTE2: Before gluing the bottom piece of wood in place, pre-drill holes and install hooks if you plan on hanging a bag/container in your vault.

NOTE3: If you want a shelf or other type of compartment inside your vault this is the time to build it.

Step 6: Magnetizing the Vent

Use the 2-Part Putty Epoxy to secure at a minimum one magnet in each corner. Obviously, the larger the vent the more magnets are needed to hold it into place. (See image above, for where I added the magnets to the adjustable 16"X6" vent.

TIP: Ensure the surface of the magnet is at the proper height to be in contact with your wall when placed over your vault. You want the magnet to just touch the wall, and not be too high or too low.

Step 7: Install Screws in Frame

  1. Dry fit the vent into the opening
  2. Mark the vent corners on your wall (light pencil marks so they can be erased later)
  3. Remove the vent
  4. Measure inboard of your corner marks the same amount as where you attached the magnet on the vent. This mark will be where you install the countersink screw that the magnet will be attracted to.
  5. Self-Tapping Countersink Screws are recommended as they will easily go through the drywall and then also go into the wood without damaging either and also not "walking" as we need the location to be precise
  6. Test fit the vent into the finished framed out opening. Add more magnets/screws as needed.

TIP1: If you have more than the 4 corner magnets, use painters tape on the exterior side of the vent to mark the location of each magnet. Then transfer those marks the same way as above but double check the inboard dimension and mark accordingly.

TIP2: Even though we are going into drywall do NOT set the screw below the surface as you normally would when hanging drywall. You want the magnet preferably in direct contact with the screw head. Any separation will lessen the strength of the magnetic bond. So, the screw head flush to the drywall surface is the goal.

Step 8: Final Touch - Fake Screws

  1. Take the screws that were supplied with the vent and cut off the majority of the length. Leave only two or three threads below the head.
  2. Install the screws in their holes in the vent, and use tape to hold them in place on the outside of the vent
  3. Flip the vent over and use more of the 2-Part Putty Epoxy to permanently attach the fake screws to the vent

Step 9: Finished

All done. So is this a real vent or my in-home vault? I guess only I will ever know.

Thanks for taking the time to read through my Instructable. Please send me any questions or comments you might have. I try to answer them all. Stay safe and healthy! Happy Hiding!

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