For those that might be new to this: take a small nail and punch a small hole (~1/8" or less) in the center of the lid. Cover this with a strip of vinyl electrical tape with a "courtesy tab" ( folded over edge). Center the lid on the jar without the band and, using the correct size attachment, vacuum it down. The electrical tape will act like a valve and allow the air to escape, then be sucked into the hole and act like a seal...to release the vacuum, simply lift the tape.
The band is optional. You can re-use the lid and tape many times as long as the sealing area is kept clean. Bands and lids are readily available, of course. Some throw-away jars are re-usable, too, as long as the attachment fits.