A vacuum device is a cylinder, which is usually plastic that you place over the penis.
Attached to it are a pump and a specially designed constriction ring. Using the pump removes air from the cylinder and the fall in pressure pulls blood into the penis like a sucking action. When the penis is stiff, the ring helps to hold the erection. To have intercourse the cylinder is removed leaving the ring in place. The ring should not be left on for more than 30 minutes.
These are also available on Schedule 2. There are many types available.