Flypaper was paper coated with a sticky, sometimes poisonous substance used to catch flies.
In 2266, Spock suggested that Balok's cube might be either a marker buoy or "flypaper." (TOS: "The Corbomite Maneuver")
When the USS Enterprise was held by Vaal's tractor beam in 2267, Montgomery Scott described the situation as being like a fly caught on flypaper. (TOS: "The Apple")