Cock Rings. These rubber donut-shaped devices tightly encircle the erect penis. Typically used to help maintain an erection, they also provide a small–temporary–size boost. Flaccid or erect, blood circulates in and out of the penis. One of the veins that carries blood out runs close to the organ’s skin (on top). A ring restricts outflow somewhat by compressing this vein. Don’t expect miracles. Any effect is modest and temporary.
Penis pumps. These plastic tubes create a partial vacuum around the penis. The vacuum draws blood into the organ, resulting in temporary size enhancement. Models differ, but all include a plastic tube and a pump operated by a hand bulb. You squeeze the bulb, which evacuates air from the tube, drawing a little extra blood into the penis. Just remember, the effect is modest and temporary.
According to Michael Castleman (a San Francisco-based journalist who has written about sexuality for 36 years), these are two temporary methods used for penis enlargement. Care to add some more?