No trench. No concrete truck. Just your mailbox, standing tall over the 4×4 that is already in the ground, in about half an hour.
Some upgrades ask for a shovel and a lost weekend. This one does not. The Adoorn 43" Slip-Over Post drops straight over an existing 4×4 wood post, so a tired old mailbox becomes a clean, modern one in an afternoon. Powder-coated steel, weatherproof, and the same considered lines as our in-ground posts, without breaking ground.
The idea is simple. The steel post is a sleeve: its open bottom slides down over the wood post, and its closed top carries the surface plate and your mailbox.
No post in the ground yet? Set a treated 4×4 first, then follow this guide. For a full concrete-set post, see the 51" In-Ground Post installation guide.
If your 4×4 is already set, this is a 20 to 30 minute job. Lay everything out first so you are not chasing a dropped screw in the grass.
What is included
43" Slip-Over Post, powder-coated steel, fully assembled
Surface mount plate for the mailbox
Four 5/16" mailbox screws and install card
Tools you will need
Wrench or socket wrench
Level, 24 inches or longer
Measuring tape
Pencil or marker
The whole install in one motion: the steel sleeve drops over the 4×4 you already have.
02USPS placement
Height and setback, before you mount.
Contact your local post office to confirm placement and height. Every route is a little different, and your carrier needs to reach the box safely from the road.
Height from road
41"–45" from the road surface to the mail entry point
Setback
6"–8" from the curb or road edge to the mailbox door
Post location
Middle of the post 16"–18" from the road edge
These are general guidelines. Your local post office may have specific requirements for your street, so always confirm before you start.
03How it works
It slides on. That is the whole trick.
The open bottom of the 43" post slides over the top of the wood 4×4 and down until the steel base reaches ground level. Because the post is 43" tall and sits at grade, the mailbox mounting surface lands right in the USPS 41"–45" window on a standard curbside setup. Confirm your own measurements before mounting.
The steel post sleeves over the in-ground 4×4 and seats down to grade.
04Step 1 · Slide it over the 4×4
Check the wood. Then let it drop.
Confirm the existing 4×4 is solid, plumb, and not rotted. Check two sides with your level. A leaning wood post passes that lean straight to your mailbox, so fix it now.
Line up the open bottom of the Slip-Over Post with the top of the wood post and lower it straight down until the steel base reaches ground level. Keep it square to the road as it goes on.
Lower the sleeve until its base reaches grade, keeping it square to the road.
05Step 2 · Mount the mailbox
Inside the mailbox, through the plate, into the post.
01Set the surface plate
Place the surface mount plate on top of the post and set your mailbox on it, lined up so the door faces the curb. The short side of the plate runs parallel to the door.
02Drop the screws from inside
Find the 2.5" x 2.5" universal mounting holes on the mailbox floor, marked with an "X." From inside the open door, push each 5/16" screw down through the mailbox floor, the plate, and into the top of the post. Start the first by hand.
03Tighten in a cross pattern
Snug each screw with your wrench, working in a cross pattern rather than around in a circle. It keeps the mailbox flat and even as each screw pulls down. Snug is enough.
Mounted and square to the curb: the finished look.
Finished
No trench. No concrete truck. Just a mailbox that looks like it was always there.
Your address is easy to find, your mail is secure, and the whole setup reads clean from the curb. That is the Adoorn way.
The finished curbside setup, mounted over an existing 4×4.
06Care & maintenance
Built to last. A little upkeep goes a long way.
Re-tighten
Re-snug the mailbox screws after the first week, then once each season. Wood and hardware move a little with the weather.
Preserve the finish
Apply a clear car wax to the powder-coated steel as needed to protect the color and coating.
Touch up damage
If bare metal becomes exposed, apply a protective paint (such as Rust-Oleum®) promptly to prevent rust.
Clean
Mild soap and water. That is it.
07Complete the look
Address numbers, easy install.
Finish the curb with 4" Mailbox Numbers so carriers, guests, and emergency services can read your address at a glance.
If your 4×4 is already in the ground, most homeowners finish in 20 to 30 minutes. Setting a new wood post first adds time for digging and concrete cure.
What size wood post does it fit?
It is designed to slide over a standard 4×4 wood post. Confirm your post is a true, un-warped 4×4 so the sleeve seats fully and sits flush at the base.
Do I need concrete?
Not if you already have a solid 4×4 in the ground. The Slip-Over Post is a no-dig mount. You only need concrete if you are setting a new wood post first.
Will USPS deliver to a Slip-Over Post installation?
Yes, as long as the mailbox meets USPS height of 41" to 45" above the road and setback of 6" to 8" from the curb. Confirm placement with your local post office before mounting.
Can I remove the post later?
Yes. Lift the steel post straight off the wood 4×4. It re-installs the same way on a new post if you move it.
Do I need to call 811?
Only if you are digging to set a new 4×4. Sliding the post over an existing wood post does not break ground, so that step does not require an 811 call.
09Quick reference
Specs and numbers at a glance.
Mount type
No-dig slip-over sleeve for an existing 4×4 wood post
Post height
43", powder-coated steel, black
Install time
About 20–30 minutes over an existing post
Mailbox height
41"–45" from road surface to mail entry (USPS guideline)
Setback
6"–8" from curb or road edge to mailbox door
Post location
16"–18" from road edge
Mailbox hardware
Surface plate plus four 5/16" screws (included)
Setting a new post
Call 811, use a treated 4×4, cure concrete 24–48 hours first
