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Restrictors, often called Thumpers by Resistance members, are tall, monolithic structures used by the Combine to deter antlions. Using a heavy piston, they send strong vibrations into the ground which frighten and ward off antlions. They are used along coastal areas and near Nova Prospekt.


Restrictors are highly effective at deterring antlions. Whenever the hammer hits the ground, they will jump back and stay out of the radius of the vibration. The heavy central piston will lift up above the ground, before dropping back down to deliver a powerful vibration.

They are deployed by the Combine, but Resistance members often use them for protection in antlion infested areas, or during their spawing season.

The most common restrictor type, found along the Coast near Combine-controlled areas as well as in some Resistance bases, is relatively small, but still effective. The ones seen around Nova Prospekt are larger and presumably more powerful, with their activation switches located at the top of a ladder.

The Combine use restrictors extensively in antlion-infested areas, placing them in strategic positions to prevent them over-running important areas.

The Restrictors however, cannot fully deter the Antlion Worker due to them having ranged acid attacks. Thus, the player should always kill these Antlions first when encountering one near a Restrictor.


Half-Life 2[]

Throughout the course of the chapter Highway 17, several restrictors can be seen along the coast, used to keep the abundant antlion population in that area at bay. Some, like the one at New Little Odessa, are used to keep antlions out of more populated or mission-critical areas.

While crossing the antlion-infested beach in the chapter Sandtraps, one restrictor can be found, but it is not operational. In order to get it working, Gordon is required to find and activate a generator trailer some distance away. It is notable that this restrictor is among the few items that are powered indirectly.

Nova Prospekt is surrounded by a network of restrictors to keep the antlion hordes at bay. When Gordon Freeman attacks Nova Prospekt with the antlions in his control, he is required to disable a number of the devices to allow the antlions to assist him.

Half-Life 2: Episode Two[]

When emerging from the Victory Mine, Gordon finds a large open area containing a lift up out of the valley. Three switch-less restrictors can be seen in the area. their purposes are revealed when two Antlion Guards rush out from the mines and begin attacking. Gordon must use the area protected by the closest restrictor for protection from the antlions, the makeshift metal building surrounding one of the Restrictors also protects from objects flung by the guards. In addition, one of the overrun Resistance outposts inside the Victory Mine contains a switch-less restrictor.

Behind the scenes[]

  • In the early stages of Half-Life 2's development, the thumper was also to have a portable version. It can be found and used in the playable Half-Life 2 Beta, where a yellow fire hydrant is used as a placeholder model.[2] It was simply named "Portable Thumper".[1] The player was to carry only one at a time and put it on the ground to achieve the same effect as the larger, stationary version. A second model, not appearing in-game and named "heavy", was probably a more powerful version.[2]
    • It was to presumably appear in Half-Life: Alyx as well. While no models of it exist in-game, six audio files in a folder called thumper and a file named soundevents_mechanical_units.vsndevts_c exist.[3] In that file, six sound events that were to play these sound files start with "MiniThumper".
  • In early Wasteland maps, brush Restrictors can be found.[4] They also appear as models in the playable Half-Life 2 Beta files, with the hammer being a separate model.[2]


  • In older versions of Half-Life, similar devices appear on Xen. While their structural appearance is different, both emit vibrations through the ground.
  • The City 17 Logo Can be seen on their bodywork, despite all Restrictors being seen notably far from City 17.
  • Combine Restrictors appear to be operate on their own power source, as in Episode 2, the player finds three still working restrictors and ultimately uses them for protection against the Antlions despite the Citadel being destroyed at the end of Episode 1.




Half-Life 2[]

Half-Life 2: Episode Two[]

List of appearances[]


  1. 1.0 1.1 Playable Half-Life 2 Beta files Cite error: Invalid <ref> tag; name "HL2Bpf" defined multiple times with different content
  2. 2.0 2.1 2.2 Playable Half-Life 2 Beta
  3. https://hl2-beta.ru/index.php?topic=29056.0
  4. WC mappack