Clothing, quilts etc. should be fully dry and folded into a convenient storage shape before put into the bag, and should leave a few centimeters from the sealed zipper.
Pull the slider slowly , and leave 1/3, then press the bag to let most of air out of the bag, finally quickly close the zipper and press the zipper back and forth several times to make sure it is completely sealed.
Open the valve cover, aim the pump to the valve mouth, pulling the piston to pumpdown. After pumping, cover the lid and you can see much space is saved.