The web-guns were weapons created by the Yeti during the Great Intelligence's third attempt at invading Earth. The weapon fired a concentrated string of strong web material. When attacked with grenades, the Yeti could use the guns to cocoon them.
The Yeti also used the guns to spin a giant web that ensnared the Doctor's TARDIS. (TV: The Web of Fear)
A Yeti web-gun was part of the shipment of salvaged artefacts given to the CIA. (PROSE: The Men Who Sold the World)
