What kind of doors should you have? Edit
When constructing your fortress or modifying existing structures it is key to remember the doors. Your doors must provide ease of access to your survivors but deny entry to the undead and bandit as well.
The first thing you should concern yourself with is that each external door should have no glass on it and be solid. A small port can be constructed around head height (approximately five feet to six feet high) but this port should only be about seven inches wide and about two two to three inches tall. This will allow you to strike outwardly against any zombie that is at your door with a spear or pike but also not allow it to break open your defensive shell.
The second major concern with external doors is that it should open outwardly. An inward opening door can be overpowered and pushed open by a large number of undead and it will hinge that way. Furthermore an inward opening door can be pinned against a wall and be quite difficult to retrieve and then push it closed. The reason an outward opening door is preferred is that the door frame provides additional support and that you can easily fortify the door while not sacrificing the ability to open it.
Materials for door should be heavy woods and even metal if possible.
A large, heavy door that has no glass, has a spear slot, and hinges outwardly will do well for defending your fortress but some modifications are reasonable and easy to install.
boarding up the door is reasonable if it is not an access and exit point. I recommend having a main entrance that serves as the entrance and exit. and then two emergency exits and entry points. every other door should be boarded up. when boarding up it is advised to board up the door from the inside. not only does this prevent the door from being forced open, it provides an extra layer of protection should the door be opened from the outside and finally it allows you access to the boarding materials from the inside of your fortress in the case that you need to repair another area.
first start by placing two by fours long ways across the door way, use large screws to place these. make sure there are at least two screws in each end of the board and reinforce it twice along the length. This should be used at around every two to three feet of height according to your supplies.
the second modification you should consider is installing several chain locks along the door. These do not add any defensive capability to the door primarily but adds an additional layer of security should the door be knocked off the hinges. These locks should be closed at all times. I recommend that at least four chain locks should be installed along the sides of the door and two should be installed above the door frame.
"Air Locks" Edit
When constructing a fortress from scratch you may want to install air lock doors on the exterior. These will allow for safer entry and exit even if there is a horde at your doorstep. these are more or less a hallway with four doors within it. the outermost door leads to the exterior and the most interior door leading to the inside of your fortress. Each of these doors are controlled by a panel and cannot be opened manually. It is recommended that these doors lift vertically. the way these doors are used is like this. the first door is opened and who ever wishes to enter comes in. once they are in, the door is closed. at this point it is the responsibility of the entrant to dispatch any undead that may have followed them in. once all undead have been dealt with, the second door opens. once they are in, a team of two will inspect the survivor for any signs of infection such as bites or scratches. If they pass they may now enter the third door, in this space they are to hand over any non authorized materials to a team that is in this area. this may include weapons or radios. after this they may enter the fortress.
Similar techniques can be applied to gates to allow vehicles to enter and exit your fortress in a safe and efficient manner.
Where can you find these doors and supplies? Edit
Each of these supplies can be found at your local hardware store. the supplies you will need are a power drill or two, several packages of large screws, lots of two by fours and the chain locks. most of these will already be around the house but can be quickly acquired by a raiding party. The doors will be difficult. It is more beneficial to select a fortress site that already has optimum doors than it is to try to replace doors.