Let Thy Window Be True - Granbury Door & Window

Let Thy Window Be True


Window guys use funny words.  Level, plumb, square, and true.

Are these words from Proverbs?  “Let thy window be level and true, elst thou shalt have leakage.”

“Those who respect their plumb and square shall prosper long in their days without leaks during the tempest.”

While our window guys may treat these concepts almost religiously, we can demystify them for you.  Let’s take them one at a time.


I think we all know this one.  Picture a flat, straight, horizontal line.  We check the level, with – yup, you got it – a level.  Usually, level is checked on the bottom sill.  At the top, or other key parts that have a possibility of adjustment during installation.  If the bubble is evenly spaced between the lines, you have level.


(Not plump – no chubby windows here.)  Plumb is when a vertical line is perfectly vertical.  It can also be checked with a level.  A level works good for larger fixed items, like doors, masonry walls, long gutter downspouts. 

Plumb is important.  Ever have a refrigerator door that if you don’t close it solidly, will slowly reopen, leaving your precious Bluebell ice cream a melted blob?  That’s a door that isn’t plumb !  Many folks adjust the feet of their fridge to make it slightly out-of-plumb to the rear, so an open door will slowly close itself.  (5-year-olds, anyone?)  In the door installation world, we occasionally are asked to adjust a door this way.  However, most people want their door to stay where they put it – open, almost shut, ajar (love that word), or just-open-enough-to-read-but-still-hear-the-kids.  If you want a door to always close – well, that’s what door closers are for (different post). 


The right tool to check square – is not a square.  Sure, we all have one of those 90-degree metal tools in our box.  You know, the one that gives you the huge gash in the back of your hand when you reach in your toolbox without looking.  (Nope, never happened to me, why do you ask?)  That’s the square, but it is usually far too small to check your beautiful picture windows.  The right tool is a measuring tape !

To check square, measure the diagonals on your window.  Top left to bottom right, and top right to bottom left.  Be careful to measure at the exact same markers symmetrically.  The measures should be identical.  If not, the window may have an undetected pressure on a side or corner, causing it to be pushed from a rectangle into a parallelogram.  (Haven’t used that word since the SAT, right?  Us glaziers R smart.).  Even a sturdy window can be misadjusted into non-squareness.  On a rare occasion, a window might be manufactured slightly un-square.  It takes a good glazier to recognize this, and return or repair the window.

That said, sometimes an installation site isn’t level or plumb or square.  Think of an old house that has settled.  The walls could be leaning a few degrees.  Installing a door or window requires careful measurement, a discussion with the builder or owner, and a conscious decision on how the installation will be performed professionally to operate correctly, and keep the air or rain out.  Sometimes it is best to fix the wall, but that can be expensive, so we make up for the imperfections with the door or window installation.  Again, an experienced window team can overcome the challenges of “existing conditions”. 

Which brings us to…


Mama said sometimes the truth hurts, but not here!  True is simply that the conditions of level, plumb, and square are all met.  True = level + plumb + square.  We glaziers live for “true.”  True is good.  True keeps the rain out.  And for window guys, True puts food on the table. 

Do you need a window adjusted?  Is your door not performing right?  Give Granbury Door and Window a call – we’ll true it up for you.

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