Haven't read this yet, but here's the thing about forcible entry that might surprise a lot of people. Many doors are much easier to force than you might naively expect. Even with a deadbolt.
Think about it like this... say the bolt extends into the jamb by a full inch. That means you only need to move the door frame by half an inch, and the door by half an inch, or some equivalent combo. But here's the rub... many doors aren't well installed or the frame has warped, etc. and the bolt does not extend into the frame by an inch. It might be half an inch or less.
So, insert a decent sized prybar (halligan bar, or flat pry bar, whatever. Sometimes a big screwdriver will do) and pry... it doesn't take that much effort to get the door to flex a quarter of an inch and the frame a quarter an inch, and bob's yer uncle.
This is really true on wooden doors/frames on residential construction. It's a little less true for something like a steel door set into a steel frame in some kind of commercial building, but there still tends to be a little bit of give which can be exploited.
Think about it like this... say the bolt extends into the jamb by a full inch. That means you only need to move the door frame by half an inch, and the door by half an inch, or some equivalent combo. But here's the rub... many doors aren't well installed or the frame has warped, etc. and the bolt does not extend into the frame by an inch. It might be half an inch or less.
So, insert a decent sized prybar (halligan bar, or flat pry bar, whatever. Sometimes a big screwdriver will do) and pry... it doesn't take that much effort to get the door to flex a quarter of an inch and the frame a quarter an inch, and bob's yer uncle.
This is really true on wooden doors/frames on residential construction. It's a little less true for something like a steel door set into a steel frame in some kind of commercial building, but there still tends to be a little bit of give which can be exploited.