A person of the criminal sort adept at finding his or her way into or out of a building. Usually someone of small stature able to fit through tight places.
Exemplified in Michael Crichton's "The Great Train Robbery" in the character of Clean Willy.
Pierce: "You say your the fastest, bloody best Screwsman in the country, hmm? Well, here's a fitting challenge!"
Agar: "Challenge? Seventy five seconds for two keys! It's nigh impossible!"
Pierce: "What if a snakesman comes over the roof and cracks the drum from the inside?"
Agar: "What snakesman's to break that drum? Nobody good enough is out. The best is Clean Willy, and he's in."
In even higher demand than fishscale, snakescale comes from the devil with no middle man in the way trying to get himself a taste.
Cokehead one-Got us a fat gram and a paramedic!
Cokehead 2-Why'd you bring him I don't want somebody I don't know watching me, you might as well bring a cop.
Cokehead 1-Nah, it ain't like that I brought a paramedic cuz its snakescale man, he's gonna give us a ride to the hospital when we finish our gram so we don't have heart attacks bro!