We installed these shades on the flat surface of our skylights, which neither were true rectangles.
Measuring: I measured my own blinds!
Installation: I installed my own blinds!
We installed these shades on the flat surface of our skylights, which neither were true rectangles. We had to add magnetic strips tp some of the rails, to accommodate for the variations in the skylight shapes. All in all, these shades do a very good job in blocking light, both through the shades, and the rails. I had little to no prior experience installing cellular shades, much less overhead on a skylight. Take your time, make sure you measure 3-4 times to be as close to accurate as possible. The way that these shades are designed and built did allow for modifications to fit our skylights. We would recommend these shades to others, as well as Blinds Chalet.