Placing the mattress in the bag is no trouble at all. Even one person can do it.
For the vertical method, simply place the bag over the mattress when it's in a standing position.
For the horizontal method, you can either start by placing the bag over the mattress whilst it's still in a flat position on the bed; or you can completely open the bag on the floor with the three sides unzipped to place the mattress on top. Then just zip the bag closed. The zip goes all around 3 sides. The reason the zip does not go along the bottom is because some people like to drag the mattress along the ground. On each bag, there are two zip pulls that meet when the bag is zipped closed.
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