ISS Enterprise caught in a Tholian Web while cloaked
A Tholian drydock containment web
A Tholian web was an energy net that was "spun" by Tholian spacecraft around an immobilized enemy vessel. The more vessels that were used to generate the web, the faster it was deployed. A web could be disrupted by destroying the ships creating the web before they finish. (ENT: "In a Mirror, Darkly")
The web was composed of a series of energy filaments which were generated in a web pattern around a target vessel. Once these filaments were sealed, the web became self-generating and the web-spinning crafts no longer needed to maintain the web. If any craft within the web attempted to leave, they would be shredded by the energy filaments. Weapons fire, such as photonic torpedoes, were also destroyed by the web and the resulting detonation energy was dispersed across the energy filaments. (ENT: "In a Mirror, Darkly")
In 2155, the ISS Enterprise was destroyed while caught in a Tholian web. Several escape pods from the Enterprise were also destroyed as they attempted to traverse the web, although some were able to leave through the gaps. The Tholians proceeded to form another web over their docking portal to prevent surviving Enterprise personnel from escaping aboard the USS Defiant; however the Defiant destroyed the Tholian ships and escaped. (ENT: "In a Mirror, Darkly")