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 terms 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.

Doors 101 - Level


The best way to describe LEVEL is to imagine a straight line that is perfectly horizontal.  Take a look at the picture above, 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, the sash will not seat up properly with the weather-strip seals.  As a result, you risk losing the Energy STAR rating your door or window came with.

Doors 101 - Plumb


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

Doors 101 - Square


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.  This 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 above for a visual explanation of SQUARE.

Doors 101 - True


By far, the most forgotten term of a door 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 above describes TRUE.  A door or window can be installed 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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Door Installation 101

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