Penis rings are very popular in the world of sex toys for men. If a professional is not in reach then a man may use a DIY version; However, it is important to ensure that whatever is used can be removed easily and quickly and is not so tight that there is pain or damage.
Although some men use rubber bands, they can be very compressed and difficult to remove. A better bet is to use a piece of ribbon and tie it around the limb. It is soft on the skin, allows the user to determine the appropriate amount of tightness and is usually easier to remove.