To keep open plastic bags of food like popcorn, frozen or dried vegetables, rice, etc.:
Some food-saver bags are crimpled, that is, have a certain texture to them. There is a reason for this, but such bags accompany vacuum-packing machines and can be very expensive. Less expensive bags (or rolled material) are sold, after-market, that may not work well or at all.
The problem is that bags without the texture may impeded air flow during the vacuum cycle. The solution is to ensure the passage of air from the food to the area of the machine performing the vacuuming. This can be achieved by cutting a small strip of the original, textured bag material long enough to reach from the food at least up into the vacuuming orifice of the machine.
Similar solutions to open an air passage will work too, but saving a bit of the premium product seems to work best.
"Polish" the rim of one end of a can on a smooth-ish concrete surface. Eventually (pretty quickly) you will wear the rim down until the lid on that end is freed. Carefully pick the can back up, perhaps sliding something underneath to keep the lid from coming off and losing the contents.