Many people tend to overlook the most basic defensive unit in the game: the lowly Farm. With 400 hit points and 20 armor, a Farm can take a lot more damage than any unit, wall, or tower. Farms can be quickly put into position by repair building and kept alive by repairing. They cost 500 Gold and 250 Lumber to build, which is about the same as a Scout Tower. More importantly, they're a necessary part of any town- you can't stage an offense without them. Since you're going to build Farms anyway, don't hide them away in the corner- use them to block off possible attack points around your town. Back up the Farms with Towers and/or ranged units to pick off anyone who tries to break through. The only drawback of using Farms is that it only takes One Goblin Sapper to destroy large numbers of them depending on how you build and protect them.

Buildings such as Barracks make even better walls because they require 2 Goblin Sappers to be destroyed while also being useful for making units at a faster rate. When resources are available use Barracks.

How Units Pop Out of Buildings
Before you begin walling in, you'll need to know exactly how your units pop out of Town Halls and other unit producing buildings.

Units come out in a counter-clockwise manner starting with the top left corner. They try for top left, if that position is filled by something, then they try the next available position in a counter-clockwise manner. If you will notice, your Peons pop out of the Town Hall when you train them in the top left corner. If someone is standing there, they pop out somewhere else. By placing buildings, walls, or units, you can manipulate where something pops out. When peons come out of making a building, or units are trained, they will ALWAYS come out in this order:

It's not quite so predictable for Peons mining or harvesting wood when coming out of the Mine and Town Hall since sometimes I get peons coming out of the wrong side of my hall.

Basically, a unit will try to come out at 1. If that's taken, he'll try to come out at 2, and so on. If all are taken, he'll pop out as close as possible to the building. For larger (3x3 and 4x4) buildings, the order of numbers still applies.

Now that you know where units pop out, you can position your buildings so that units will pop in our outside your wallin. It's much easier to wallin when the enemy is facing toward the left side of the town because your units will pop out of the barracks on the left side.

Basics
Completely wall-in Peasants on Gold and Lumber leaving one or more on the outside to build more Barracks and buildings when space fills up inside the wallin and to build expand at other resource nodes. Use the Barracks as one of the buildings to complete the wall in or make sure that the Barracks troops will pop out on the outside of the wallin. You may put up your Lumber Mill on the outside or inside depending on space. All Peasants on the outside can either chop or build buildings.

The wall-in plan is not designed to allow you to just sit around and wait for them to attack but instead as a way to provide defenses for your workers while still being able to attack the enemy. The wall-in plan is only useful until about the Stronghold stage. As the Stronghold/Keep stage is reached Goblin Sappers are readily available which can allow the enemy to quickly blast their way into the town.

Examples

[ Click to Enlarge - 67 KB ] 3 Farms and a Barracks are used to wall the town in. The Barracks opening is placed on the outside so that when units pop out, they pop out in the direction of the enemy instead of inside the town.	[ Click to Enlarge - 68 KB ] A completed Grunt pops out of the Barracks and is ready to further support these defenses against attacks on the Peons mining Gold. Be careful when building the Barracks to leave the left side open so that units will pop out and be able to go attack the enemy.

[ Click to Enlarge - 65 KB ] A Peon builds walls between the Farms so that Goblin Sappers cannot destroy more than one Farm at a time. Grunts are placed around the Barracks blocking the empty spaces so that when a Catapult is trained it pops out on the inside of the wallin. Walled in Catapults are extremely effective as the enemy has a very hard time busting into the town while under attack. The next worry for this town is Bloodlusted Ogres, Sappers, Blizzard and possibly Catapults if you're unable to defend the front of your town with your Barracks units. A Guard Tower is built behind the Farms leaving plenty of room for Peons to get in behind to repair the Farms and Guard Tower if they are attacked.

[ Click to Enlarge - 77 KB ] A Peon builds walls in front of the Farms to prevent Sappers. A Barracks is built in front of the walls further adding to the layers the enemy must get through to get into the heart of the town.

Walling In On the Left Side
Units pop out on the left side unless it is blocked so walling in on the left side of the map, or when the mine is left requires more care and often more buildings. You also have to be more careful place Peons on the outside before walling in or you will as getting stuck in your town is more common when you have a mine facing left of the Town Hall.

[ Click to Enlarge - 60 KB ] The Town is walled in. The Barracks is placed in such a way that the units pop outside even though they come out left of the Barracks.

Don't Leave Any Holes
To be fully walled in make sure there are no holes where the enemy can sneak through to get into the town.

[ Click to Enlarge - 78 KB ] An enemy footman pushes his way into the Town through a small hole.

Don't Wall Enemy Units Into Your Town
Before completing walling in make sure there are no enemy units inside. Occasionally you will find some players that will accidently wall your units attacking them into their town which will make it even harder for them to save their town.

[ Click to Enlarge - 71 KB ] Player walls Footman into town by mistake.

Don't Chop Out Too Soon
The goal of the wallin is to prevent the enemy from getting into the heart of your town to attack either the Peons mining Gold or the Peons chopping Lumber. By adding more defense to your workers you can often survive much longer than if no defenses were set up. After you have created your walled in town, be very careful to make sure Peons do not chop a hole through the trees which will give the enemy access to your town. The effectiveness of the wall-in is immediately destroyed when the Peons open up a path through the trees into your town. If you do not watch, they will do it during their normal harvesting of the Lumber around the town. If you find an open path into your town because the Lumber has been removed, quickly fill up that space with a building such as a Farm. Then pay extra attention to make sure no further holes are created until you're ready to chop out which is usually after you're ready to take another Gold mine.

[ Click to Enlarge - 95 KB ] Peons have chopped a hole into the backside of the town so a Farm is quickly built in the hole to fill it up. Send other Peons to repair the Farm as it is built to get it into position faster.	[ Click to Enlarge - 91 KB ] Walls are built in front of the Farm so that it will take more than one Sapper to bust into the town.

[ Click to Enlarge - 61 KB ] This Peon is about to chop out, make sure that he doesn't.	[ Click to Enlarge - 82 KB ] A hole opens up making room for a flood of Bloodlusted Ogres.

Don't Wall Yourself Out Of Your Own Town
A common mistake is to accidently wall yourself out of your own town as an enemy attacks. Often this happens when Peons accidently chop open a hole on the other side of the town, you forget that there is more than one entrance into your town or the enemy uses Goblin Sappers to open up a path through the trees into your town. Although you may be able to walk around to get back into your town, often this is much too late as you may find all of your Peons killed. It is important to have a few Towers in the town walled in just in case something like this happens. It is very embarrassing to lose your town as you have plenty of troops available to defend it that can't easily get inside the town to defend it.

[ Click to Enlarge - 76 KB ] Grunts are unable to defend their own town.

Make Sure You Have a Peasant or Peon Outside
Another common mistake is to wall yourself and all Peons into your town. Then when you need to build more buildings on the outside or head off to build at another mine you have wait until you chop your way out. This can often put you behind in resource gathering and sometimes prevent you from being able to set up at a second resource spot before the enemy. Before completely walling yourself in, place one or more Peons on the outside. Hide them if possible so the enemy doesn't kill them. Be warned if you place them on chopping Lumber on the outside, when they return to the Town Hall they may pop on the inside of your wallin, leaving you stuck.

[ Click to Enlarge - 67 KB ] Leave a little section of trees so that it's easy to chop out. But watch out, the enemy may just blow a hole through the trees with Goblin Sappers.	[ Click to Enlarge - 80 KB ] Once you have chopped out be sure to fill up the hole with Farms and Walls.

Breaking Through Wall-Ins