Sidetracks are a snap to install, and measuring is nice and easy, too! What makes the measuring process different from a non-sidetrack measurement is the length you order and that you should check first to make sure your window is square.
Measuring For Squareness:
Take the diagonal measurements by measuring from the top left corner to the bottom right corner and from the top right corner to the bottom left corner of the inside of your window frame. Write down the measurements as you go. If the two diagonal measurements are within 1/4" of one another, then your window is sidetrack-ready! If the measurements differ by more than 1/4", then your window will require some shimming before it can properly accomodate sidetracks.
Measuring to Order:
Width: Measure the inside of the window frame in three places: the top, middle, and bottom. Write down your measurements as you go, and mark the narrowest width you took.
Length: Measure the inside of the window frame in three places: the left, middle, and right. Write down your measurements to keep track, and then mark the shortest length that you measured.
Make sure that your three widths are within 1/4" of each other. Even if the diagonal measurements are within 1/4", some windows can throw you for a loop and have widely differing widths anyway. If you find that your widths are greater than 1/4", you'll want to shim the wider parts so that the shade rides along the sidetrack as tightly as possible.
For added peace of mind, double check your measurements and be sure to reach out to a member of our team if you have any questions.
Print Measuring Guide for Sidetracks. (link)