What do they really mean?

Our clear-cut explanation of Level, Plumb, Square & True.

We hear these words used all the time, but have you ever taken the time to really think about what they mean? Equally important, these words can have a major impact on your next door or window installation. Take a read below to make sure your fenestration terminology is up to par.


The best way to describe LEVEL is to imagine a straight line that is perfectly horizontal. As you can see in the picture below, the dotted green line represents LEVEL. If a door or window is installed out of LEVEL, it will tend to rub on the jamb and it will be hard to get the reveal (spacing between the door and frame) to line up. If the reveals don’t line up, you risk losing the Energy STAR rating your door or window came with because the sash will not seat up properly with the weather-strip seals.


To visualize what PLUMB represents, take a look at the dashed green line below. PLUMB is the term used to refer to a perfectly vertical line, thus why we call the clever tool used to find PLUMB a plumb-bob. If a door or window is installed out of PLUMB, it will cause a host of issues: sagging open in the corner, unwanted opening or closing doors, and binding during operating.


The definition of SQUARE is a 90 degree corner. A speed square, framing square, and T squares are all good examples of tools used to find SQUARE on a jobsite. Installing a door or window SQUARE involves being both LEVEL & PLUMB at the same time and is important to prevent: binding during operation, springing open on the corners and again to insure proper sealing between the sash and frame. Take a look below for a visual explanation of SQUARE.


By far, the most forgotten term on an installation, TRUE represents being SQUARE on both the LEVEL & PLUMB axis at the same time on all sides of the unit being installed. The picture below describes TRUE. You can install a door or window perfectly LEVEL, PLUMB & SQUARE on one side, but if the other side’s aren’t LEVEL, PLUMB & SQUARE, the unit will not be TRUE and will create many of the problems mentioned above.

These terms are hard to differentiate at first, but by gaining a good understanding of LEVEL, PLUMB, SQUARE & TRUE you are sure to get better results out of your next installation.

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JENTRA door levels

One thing has stood out clearly to us in our combined 15 years of experience in both the sales and installation of residential/commercial doors…. the lack of accurate door installation happening in the field. This installation process has been virtually the same since pre-hanging started in the 1960’s and yet it’s not uncommon to find a poorly installed door on most jobsites. It’s time to take a new look at this.

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CHEATAH door level

CHEATAH door level

The CHEATAH™ door level kit makes installing a door simple and quick. Attach the CHEATAH directly to the top and sides of the door. The four precise levels work together to allow easy, accurate positioning of the door. Once level, the built-in shim guides let you correctly shim the jamb. The CHEATAH works on all types of doors with perfect results each time. Our door level kit is extremely durable and carries our 100 Guarantee™. Save time and money installing doors right the first time, every time. The JENTRA CHEATAH door level puts advanced speed and precision capability into the hands of all skill levels during installation, from DIYers to skilled artisans. This results in improved installation and function of doors, resulting in fewer warranty callbacks. Therefore, stakeholders of the door level include all steps in the industry: door manufacturers, distributors, contractors, and building owners.

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