Inside the window - Measure the depth and width of the window recess in a number of places (as walls are not always straight). Use the narrowest measurement to the nearest millimetre as your guide. The recess will need to accommodate the pulley mechanism and the fabric drop will be the length it hangs at its most extended. When measuring the width of the recess take a measurement at the top, middle and bottom and take a note of the lowest measurement. This ensures that the blind will not snag when in use (diagram D).

Outside the window - The blind will need to extend beyond the window width. Again, measure different points of the window width and use the narrowest measurement, remembering to add 38mm for the pulley mechanism. Then measure the drop. This will be how far the fabric hangs at its most extended. For width size measure the width of the window and add approximately 4 in (10.2cm)at each side of the window to allow an overlap (diagram E).