Hartman Hole Dome

Hartman Hole Domes in 3 sizes cover 2.5"-8" construction site holes.Hartman Hole Domes Orange, Yellow, Red Self-Adjust to Cover Holes 2.5" - 8.0" in dameterYellow Hartman Hole Dome HHD_3.75-5.5 installed in hole to prevent injuries, as required by OSHA for construction sitesCupertino Electric at LAX Before and With Hartman Hole DomesHartman Hole Dome's flexible fins allow the hole plug to adjust to diameter of hole; OSHA required labeling on hole cover top

Hartman Hole Dome is..

The Hartman Hole Dome

Our innovative hole covers easily plug electrical and plumbing holes ranging from 2.5″ – 8″ in diameter.

Hartman Hole Domes automatically adjust to the diameter of the hole you need to cover.
With no moving parts, Our hole covers are designed for quick installation and removal.

Our hole plugs fulfill OSHA safety requirements for securely covering wall and floor openings at construction sites.

Unique Features

Friction Fit – Self Adjusting

Our patented design allows each Hartman Hole Dome to self-adjust for a custom fit across a wide range of common hole diameters.

Quick Installation

Simply “Twist!” and Push to install, “Twist!” again and Pull to remove!


The Hartman Hole Dome has fins on the “plug” portion which inserts into the hole with a “Twist!” .
The fins flex to a friction-fit within the hole.
Smaller holes cause the fins to flex more.

Our innovative fins allow just 3 sizes of hole covers to fit 22 standard size holes:
From 2 1/2″ to 8″, counting at 1/4″ increments. They will also fit most dimensions in between, including metric increments. See Specs for details.

Color Coded

Hartman Hole Domes are color coded to indicate hole diameters it is designed to cover.
Covers are also clearly labeled with raised lettering at the top of each dome.
Neon Orange: ___ 2.50″ – 3.5″ holes
Yellow: ___________ 3.75″ – 5.5″ holes
Neon Red: _______ 5.75″ – 8.0″ holes

Easy Removal and Installation

Simply “Twist!” and Push into place in either direction, clockwise or counterclockwise.

Simply “Twist!” and Pull. Always “Twist!” in the same direction in which the plug was initially installed.

There are no moving parts, and no tools required.

Weight Bearing and Secure

Meets OSHA Regulations for Construction Site Hole Covers

The diameter of the top of the Hartman Hole Dome is designed to maintain a 1″ or more overlap of the floor or wall that the hole is in. The top of the Hartman Hole Dome will also overhang the outside of any pipe or conduit the plug is inserted to.

For example, the HHD 2.5 – 3.5 cover has topside diameter of 5.5″,
which ensures an overlap of 1″-1.5″ depending on hole size.

Likewise, the HHD 3.75 – 5.5 has a dome diameter of 8.0″,
ensuring an overlap of 1″-2″ depending on hole size.

This 1″ lip provides support of the hole plug to help ensure it will not be forced into the hole, pipe, or conduit the plug is protecting.


Water damage is a real cost concern during construction.

Caulking can be applied to the Hartman Hole Dome around the perimeter, and to the underside of the top of the hole plug to aid in preventing water from dripping onto the floor below.

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Purchase the Hole Dome size according to
the diameter hole you are looking to cover or plug:

HHD 2.5 -3.5  (Neon Orange) _ fits: 2.50″ – 3.5″ holes
HHD 3.75-5.5 (Yellow) _________ fits: 3.75″ – 5.5″ holes
HHD 5.75-8.0 (Neon Red) _____ fits: 5.75″ – 8.0″ holes

Installation Instructions PDF

DO NOT just force plug straight into hole or pipe. This will cause damage to the flexible fins. Always “Twist!” when installing and removing”


Always “Twist!” and Push into hole or pipe.


Always “Twist!” and Pull out of hole or pipe.



Plugs can be “Twisted” Clockwise OR Counterclockwise to Insert.
Must be “Twisted” in the Same direction to Remove.

If plug does not want to twist in the direction you turn for removal, try twisting in the other direction. There is no way to know which way the installer twisted the product at install.

For efficiency, you may want to adopt a convention of “always Twist Right” (or “always Twist Left”) to insert And remove.

DO NOT install the hole plug in holes that are not with-in the size range the hole plug is intended for.

Size range is Printed on top of each hole plug, and also is color coded:
Neon Orange: ___ 2.50″ – 3.5″ holes
Yellow: ___________ 3.75″ – 5.5″ holes
Neon Red: _______ 5.75″ – 8.0″ holes

Features Compared to other
Hole Plugs /
Hole Covers
Hartman Hole Dome Product A Product
Fast and Easy Installation YES Yes NO
One Size Fits a Range of Hole Diameters YES NO Yes
Fits Snug and Secure YES Wears Over Time NO
Waterproof to Floors Below Apply Caulk Yes NO
Consistent Performance,
Independent of Installer
Must be manually adjusted to fit each hole.
1″ Top Overlap YES NO Yes
Fast and Easy Removal YES Yes Yes


Product A

This product has no adjustments to accommodate different hole sizes.
Each item is made for one specific, exact hole size.
A 4” cover will not fit 3 ¾” or 4 ¼” holes.

The underside of this product has a foam ring around the protrusion that fits into the floor.
This foam can wear out and stay compressed. When this happens, the cover could become loose, and be knocked out of place.

This product does not have 1” of bearing surface as the “Hartman Hole Dome”.


Product B

This hole cover can be manually adjusted to fit various size holes.
However, to fit various size holes, every cover must be re-adjusted at every install.
This manual adjustment can be time consuming.

This product is not easy to use, which can result in frustration and/or non-use.
To use: The installer must slide a part along the slots in the cover until it touches the edge of the hole. This part is then tightened to stay in place. Repeat the process until all 3 slides are against the sides of the hole.
The effectiveness of this hole plug is totally dependent on the person installing it.

This item does not fit tightly into the hole it is intended to plug.
It has moving parts that must be manually adjusted to fit each and every installation.
Thus it is prone to the installer’s attention to detail.

This hole plug is physically weak due to the adjustment slots in the cover.

It is Not waterproof to floors, or the opening below its cover.
Water or liquid can migrate through the slots in the the cover.


Each of the Hartman Hole Dome hole plugs, hole covers, fits a range of common hole sizes.
For example the HHD 2.5-3.5 securely fits any hole from 2.5″ to 3.5″ in diameter.

Each Hartman Hole Dome top always overlaps the largest hole, pipe, or conduit it can be inserted into by 1″.
Covers are Color Coded, with size range printed on the top

Hartman Product Number HHD 2.50-3.5 HHD 3.75-5.5 HHD 5.75-8.0
Fits holes sized (inches) 2.50″ – 3.5″ 3.75″ – 5.5″ 5.75″ – 8.0″
Color of Dome Orange Yellow Red
Diameter of Dome 5.5″ 7.5″ 10.0″
Price / piece $13 $19 $22
Fits holes sized (cm) 6.35cm – 08.89cm 9.93 – 13.97cm 14.61 – 20.32cm


Category Product of the Year Winner

EC&M Magazine's Product of the Year Category Winner 2015 logo

featured in April 2015 issue of EC&M

featured in May 2015 issue of Electrical Wholesaling


Cut Away Showing Solid Construction

HHD 3.75-5.5 Constructed with a Machined Steel Plate inside. Weighs a whopping 2Lbs!

The smaller HHD 2.5-3.5 Is Solid. Much sturdier than hollow covers you’ll find elsewhere.

Hartman Dome cutaway showing solid construction and machined steel plate


Hartman Hole Dome in 3 Color-Coded Sizes

Hartman Hole Domes Orange, Yellow, Red Self-Adjust to Cover Holes 2.5" - 8.0" in diameter


Close Up View, Hartman Hole Dome HHD 2.5-3.5

Hartman Dome HHD-2.5-3.5 with its Patented Fin Design which self adjusts to a multitude of hole sizes



Installing Hartman Dome HHD-2.5-3.5 into a hole in cement floor at a construction site, image 7



Hartman Dome HHD-2.5-3.5 Installed into hole in floor at a construction site, image 8


Weight Bearing

Hartman Dome HHD-2.5-3.5 installed in floor with heavy machinery on top of it, demonstrating weight bearing feature of the hole covers, image 9


Hartman Hole Dome

How It Works


Bottom View of Hartman Hole Dome Installation
Fins flex to accommodate a range of hole sizes with a single plug

Bottom view of wooden board with a single size Hartman Hole Dome hole plug installed into 3 different size holes, showing how the fins flex to automatically adjust to the correct hole size

Who Uses Hartman Hole Domes..

Cupertino Electric Inc logo
Cupertino Electric
W-E-ONeil logo 198x59
W.E. O’Neil Construction

G.D. Heil Demolition Contractors Logo

GD Heil Demolition Contractors

VEM General Contractors in Hayward, CA uses Hartman Products, Hartman Hole Domes
VEM General Engineering


Hartman Hole Dome is..


Hartman Hole Dome
Designed in California, USA
Manufactured in California, USA