Walling as Terran
- This article deals with Terran Wall-ins in general. For wall-in formations on specific maps, refer to each map's article.
Walling (or "walling in", "wall-in" or "blocking") means creating buildings at the ramp or opening of your base so that enemy units can't get through. Walls are commonly seen in TvP, TvZ, and 2v2 games. They are generally built using the first Supply Depot, the Barracks, and if necessary the second Supply Depot. In TvZ, it is also common to use a Factory as a part of the wall. This quick guide will show you the basic principles of constructing a wall on any map.
 Why Wall?
Walls are a powerful tool for Terran players as they allow Terran to guard against most early rushes done by a Protoss or Zerg player. A cautious Terran player that walls every game will be safe against most early rushes, provided that he repairs the wall. There are some early builds that are designed to take down a Terran wall (such as the 10/15 Gate from Protoss), but they will generally work best on maps like Medusa, where there is no ramp for Terran to hold.
Yet one of the most important functions of walling is to deny scouting. Thus, you can constantly keep your opponent guessing in TvP and TvZ, which is vital to ensure that you can pull off any unorthodox or rush strategies in the early game.
It is important to note that your economy will be a little bit worse off if you wall than if you don't as it takes time for SCVs to travel to your wall and back to the mineral line. However, the benefits of walling are generally worth the few minerals lost due to walling.
 Building placements
 Tight against Zealots
- The key is to have the top or the right side of the Barracks edge against a Supply Depot. This way Zealots can't get through between those buildings
- Zealots can't get through 2 Supply Depots that share edges or corners
- Where the buildings edge the maps, you generally want to try to make as much of the buildings as possible to be close to the edge. The wall generally gets tight if you fit the corner of the Supply Depot and Barracks into a place where the edge of the cliff turns a little. This comes with experience though.
- The left side of the Factory against the Supply Depot will keep Zealots out.
 Tight against Zerglings
- Only the top side of the Barracks against the Supply Depot will keep Zerglings out
- Both the bottom and the left side of the Factory against the Barracks will keep Zerglings out
- Factory on top of the Supply Depot and vice-versa will keep Zerglings out
- Zerglings can't get through Supply Depots stacked on top of each other
- Zerglings can often get through around the edge where Zealots can't
 Tight against Scarabs
Walling off scarabs improves the chance of path-finding glitches by increasing the distance of the shortest path. This provides more time to maneuver units than without the wall-off, often resulting in scarabs moving back and forth until timeout.
- Machine Shop to the left of an Armory.
- Control Tower to the left of an Armory.
- Armory adjacent to mineral patch.
- Academy to the left of a mineral patch.
- Machine Shop to the left of a mineral patch.
- Armory below a Refinery.
- Comsat Station to the left of an Armory.
- Missile Turret below mineral patch.
 Testing your wall
There is a simple rule of thumb for testing your wall in-game
- If an SCV can get through, so can a Zealot.
- If a Marine can get through, so can a Zergling. However, note that the opposite is sometimes false; a Zergling can sometimes fit where a Marine cannot. Therefore, manually testing your walls with Zerglings is encouraged, or strictly following the guidelines laid out in the "Tight against Zerglings" section.
 Fixing a failed wall
If it's critical that your wall doesn't allow enemy units to pass, as in a 2v2 where you scout twenty Zerglings/Zealots coming toward you and you just discovered your wall is not tight, the easiest way is to fix it with one or more SCVs.
- Place the SCV in the exact position where units get through.
- Select the SCV together with a Marine and click Hold Position.
- Optionally, use a second SCV to repair the first.