Here is a little pictorial for how to use these bags with the Foodsaver V3800 series(upright models). The video makes it look so easy but it is not. This is how I did it on my first try
First crinkle the end of the bag that you are going to seal with your hand(this is the part that makes it harder to get into the V3800 because it is no longer smooth but you need to do it for a proper vacuum)...
Now take the mouse vac material(sold separately from the bags) and cut a piece in half...
Then insert a piece on each end of the bag where the material is almost touching the opening of the bag and flush against each edge of the bag...
Now lift the top of the food saver up using the two release buttons just like you open it when cleaning the moisture collection tray inside the unit. Then place the end of the bag just inside the unit before it touches the paddle that turns the unit on when you slide the bag all the way in...
Now gently close it on top of the bag. The bag should be just inserted into the unit...
Now using your thumbs on each end grab the fabric and bag. Now slowly slide the bag into the unit like you would a regular bag just more gently...
Once the food saver starts up verify it is pulling vacuum. Then use you hands to help move air out of the bag for a tight bond with the meat. If you do it right the food saver will reach full vacuum, stop, and then seal. I then lifted the unit up again using the release buttons and lifted the bag off the sealer carefully so I did not tear it. Keep in mind that these bags are much thinner material than the regular bags so you need to be gentle when handling them