These are a redbrand of the fowfer. You will find them in a search with that and in the PE FAQ (linked at the bottom of the page).
The concept is to pull your penis up behind a buttock (or between your buttocks if you can get it to work) and then sit down on the penis. If when you sit you bend forward, simply straightening up should cause an OK stretch. Experiment and you’ll find a good stretch.
This kind of stretch is never going to be ‘intensive’ its probably something that could be considered ADS without a device.