Spend a night with John Sharpshandler, and you’ll see why he’s the Martha Stewart of needle exchange. “You have to go in a straight line,” he says, showing a man on a Berkeley street corner how to wipe an alcohol-soaked pad from the crease in his inner elbow halfway down to the wrist. “When you rub in a circle, you’re just moving the germs from one place to another.”

With a calm, friendly voice, the 38-year-old Sharpshandler—he adopted the pseudonym in 1990 to avoid legal harassment—greets the people who have made their way to one of three local Needle Exchange Emergency Distribution swap sites on this chilly late-December evening. Almost a dozen of the syringe exchangers are first-timers and he gives them the full tour: three card tables stacked with needles, bleach kits, condoms and bottled carrot juice served out of the back of a truck. There’s also free HIV and hep C testing by the city in a van down the block. Tonight’s other 40-odd exchangers are regulars, bearing used syringes in paper bags, mini biohazard buckets, totebags with cigarette logos,

The new folks all make a point of counting out their needles—as if to prove, in this half-legal no-man’s-land of harm reduction, they’re worthy of a little trust. “I have 17,” a young man says earnestly, laying each one down. The volunteer helping Sharpshandler keep track of the numbers stops him midtally. “It’s OK, you don’t have to count them,” she says, handing him 20 clean needles in a Zip-loc. And then, kindly but firmly: “We expect to get these all back.” Trust works both ways here.

“There are several basic needles we give out, depending on how you’re hitting,” Sharpshandler explains in his characteristic mix of technical jargon and street slang. “There’s full-size, with a one cc capacity and a 28-gauge, half-inch needle. Those are probably better for people with big hands, because it’s awkward to hold the needle, tighten a tourniquet and shoot the drug all with one hand.” A big needle will help you hit through scar tissue, he continues, “but you have to be careful not to shoot clear through the other side of the vein.” For women, who tend to have smaller veins than men, Sharpshandler sometimes has a mixed bag including “kitty needles”—made for veterinarian use. “Or if you’re shooting steroids or hormones,” he says, “vaccination needles can handle those oil-based drugs.”

Sharpshandler knows that “every vein is valuable” to users, and after a decade at the exchange, he’s amassed enough information to make sure that whether or not they always use clean needles, people know how to as safely as possible. “When we have this many kinds of syringes,” he says, “it’s obvious that we really care about people’s needs and preferences. They love that.”