An apadravya is a body piercing done vertically through the glans (head) of the penis. It's known as one of the two most painful piercings a man can get (the other being a palang or ampallang; same idea but placed horizontally) and the best for improvements in sexual intercourse. Possibly inspired by the rhinoceros or some rodents indigenous to Borneo which, I'm told, have barbed penises, the first appearance of a piercing through a penis is on a bronze statue of a dog dated around 400 CE. It was first mentioned in writing in the Kama Sutra (700 CE):
"Among the people of the south there is a belief that one cannot enjoy truly intense sexual pleasure unless the lingam has been perforated.
"Now if a young man wishes to try this method, he should pierce the lingam with a very sharp instrument and then sit in water until the bleeding has stopped. The same evening he should indulge in a very active form of sexual intercourse so that the hole can be cleansed. After this, he should continue to wash the hole with various liquids and if he wishes he can make the hole larger by inserting reeds which will gradually enlarge the orifice. One can also wash the wound with a mixture of honey mixed with liquorice, and anoint the hole with a little oil.
"In this hole across the lingam one can insert any kinds of Apadravyas [nb: in this text, "apadravya" refers to a dildo-like attachment for the penis] such as: the Round (round on one side); the wooden mortar; the flower; the bracelet; the heron's bone; the elephant's goad; the eight balls; the lock of hair; and other such objects, which are named after the shapes and purposes they serve. All these apadravya should possess a rough exterior which adds to the efficacy of their use."
The apadravya first appeared in European literature in 1588 when Cavendish visited Capul:
"Every man hath a nayle of Tynne thrust quite through the head of his privie part...."
The apadravya started to appear in America in the late 1980s.
Proper placement has the piercing centered in the glans, passing between the sides of the corpora cavernosa and through the urethra, but it is possible (though not as sturdy, and harder to heal) for an apadravya to be done to either side. Sometimes (rarely) apadravyas are pierced behind the corona of the glans ("shaft apadravya").
The procedure for the piercing is pretty standardized. Sometimes piercees may have a fully healed PA piercing beforehand so as to reduce the amount of tissue that has to heal at one time (reverse PAs are done at a different angle), but this is not necessary. The piercing generally bleeds right after being pierced, but should not bleed excessively or dangerously (there are horror stories involving hospitals and uroligists and blood coming out of three holes, but they are rare). The initial jewelry will be longer than it needs to be to account for swelling and the increase in penis size due to erections, and should be around 10g to 14g. Any swelling usually goes away within a week. Healing time is around four to six months (some say healing for an uncircumcised man may take 18 months) and is not impeded by the flow of urine. Any type of sex or masturbation should be avoided until the piercing is at least two weeks old, and some recommend following the 30-Day No Touch rule — even if it feels fine, the moment before orgasm dialates blood vessels in the penis and usually causes quite a bit of unexpected bleeding when you least want it.
The apadravya does not affect the flow of urine: when the piercing is placed correctly, the piercee is still able to pee standing up. The larger gauges are said to bring a pleasant weight to the penis, and walking can be pleasurable. Those who have it all agree that it is a great addition to one's sex life, but obviously is not for everyone.
So, the question on everyone's mind: Does it hurt??
Well of course it hurts — having a huge sharp steel needle shoved through any part of your body hurts, especially your genitalia. But it's painful because of the intensity, not duration, of the pain: I've heard it described as being as brief as a moment, to as long as only a few seconds, and for me it was only muscle-twitchily painful until the jewelry went in. The healing process is not painful — tender and maybe sore, but nothing anyone can't deal with. Urination may sting for a few days until the healing really gets going. Cleaning is necessary; many sources say twice a day with a unscented liquid antibacterial soap (Dial works) and a dip or two in sea salt will have you healed up good and quick.
I've heard of people trying to do these themselves, but to only minimal success — no permanent damage, thankfully. This not a risky piercing unless your piercer doesn't know what sie is doing, so make sure you do some research before getting one done. Pictures of apadravyas (warning, pictures are graphic!) can be seen at Infinite Body (http://www.infinitebody.com/gallery/male/maleapaamp.html), and SPC (http://spc.bodymodification.com/galleries/piercing/apa.htm).
Much information comes from personal knowledge, other information gathered from experiences at BMEzine.com.
Updates:
18 October 2003: URL changed
31 May 2004: Little things here and there
17 December 2004: Added some personal experience (!), removed BMEzine URL, reorganized a bit