Measure how much to hem while the curtain is hanging (don’t pull too tightly when measuring). Pull your ironing board over to the window and measure the portion to remove using your ironing board as a craft table. Use starch to crease along the ‘to be hemmed’ portion with your iron (while they’re still hanging). Iron the adhesive strip along the fold (yep, still hanging)
Also on these boards
Tutorial on creating a template for hanging curtain rods the same height/distance every time...no more measuring & leveling over & over! Brilliant!