By Suzana Mikolova 
Hanging a door is not so easy if you don’t know a few tricks. Here I will show you the easiest way to hang a door. Firstly we have to get nearest size of door to the opening that is already there.
Doors are manufactured in various standard sizes. The manufacturers also make them in what is called in the trade as blanks, it is a solid piece of door which you can cut the size out off. There are also firms that make special sizes but they can be expensive as they are making one off a certain size.
Firstly then, measure the original door size, check with your supplier if it is available. The size you have could be metric or imperial, that is it could be millimetres or feet and inches. The old door size could be I a smaller size that is a stock size, (standard size) which is a good thing, if it is then that is the one for you.
Some times with modern buildings you will find that you don’t really have much work to do to hang and fit the new door as the frame will accommodate the size that you have because these particular frames and doors have been specially manufactured for your home when it was constructed.
The older buildings are a challenge because maybe the building itself has sunk in one place or another leaving the door frames cockeyed or skew. I have personally seen some that are 30mm out of square and that is only in the door width, say 800mm or 900mm.
If you have a situation like this, check first that the door is fitting okay, if it is. When fitting the new door and have it on the trestles put the old door (when it is stripped) on top and use the old door as a template and mark around it. This is the easiest solution when faced with this situation.
Modern doors are manufactured sometimes with a hollow core to make them lighter for the hinges. They are like a egg box inside with a solid piece running all round to make the door rigid and give it strength. Cut that away and you are in trouble.
When you get the new door home leave it in the room for about a week so that it can acclimatise to the room because this door has been in a cold warehouse until you bought it and it has to get used to its surroundings. I know it is just a door but remember it was a living breathing tree once.
The next very important thing to look for (most people don’t know this) That on the top or bottom edge of the door there is a marking symbol stamped on the door, the symbol is “LOCK “,that symbol defines the side of the door where the lock goes. In the construction of the door the manufacturer glues an extra block of timber in to accommodate the lock. On the hinged side of the door there is around 20mm of timber for the hinge screws. Bottom and top there is the same amount of thickness, if you have to cut this off you can clean the piece up and glue it back in and clamp it up till it is dry. On the lock side of the door it is the same as the hinge side but the block I spoke about earlier is only around 300mm long so it is imperative that you get this right. Get this wrong and you will have difficulty fixing the screws to the door itself as you are only fixing to the thin outer sheet of the door, you would be better to throw the door away and start again as the handles on the door is not going to stay there with the steady opening and shutting.