Ah, but it's the sort of thing you discover when you've just finished and remember you closed the door to let you get the last few floorboards in. Then you spy the saw you were going to use, but cutting the door went right out of your mind when SWMBO asked something at the wrong time...
Though much more likely is to find the heads of the hinge screws are buggered and they won't come out without a fight. Or, even worse, the bloody screw shears off at the head, and a 20 minute job suddenly takes all afternoon!