fishlining
What does fishlining mean?
The art of moving stuff between cells by tying it to a line — usually a strip of bedsheet or unraveled sock — and flicking, swinging or sliding it under doors or along the tier. The string is the 'fishing line', the package is the 'kite' or 'fish'. Bread-and-butter inside comms: notes, tobacco, food, drugs, whatever needs to travel without a guard noticing.
Origin
US prison slang, fishing imagery — the line goes out, the catch comes back. Documented in American corrections writing from at least the 1970s.