Step 1. There should be at least 1" of flat area all the way around the existing window to recieve Storm Window. The example shows approx. 2 - 3/4 "
Step 2. If there are existing blinds in place, they can still be used ; but there needs to be at least 1 - 1/8 " behind them to allow the Storm Window to pass behind it.
Step 3. Measure bottom of existing window at location of where Storm Window will be placed. Measurements should be with-in 1/16 " if possible. Tip: Draw a sketch on a piece of paper and write the dimensions in appropriate location so you don't mix things up!
Step 4. After measuring bottom, move up to the middle and measure it and write measurement in appropriate location on sketch. Tip: If this measurement is the same as Top and Bottom; no need to write it down.
Step 5. After writing middle measurement on the sketch; measure top of window at location of Storm Window.
Step 6. Now measure Left and Right side, and write this measurement in appropriate location on sketch. Again; try to be within 1/16 "
Step 7. Measure Center and write this measurement on sketch.
Tip: Like other middle dimension; if this is the same as Left and Right side; no need to write it down.
Step 8. Now measure the last side and write it in the appropriate location on sketch.
Step 9. Although "Timely Interior Storm Windows" are quite flexible and adjustable; it is important to manufacture them as close as possible to fit existing openings - using a book or a magazine as a tool to determine which corner(s) are square.
Step 10. This picture shows what an Out-of-square corner looks like; note the bottom right and lower left arrows are in contact but other arrows are away (step 9 shows a relatively square corner; only a slight gap at top side arrow).