Before buying a new door measure the height and width of the frame to determine the size of the door needed. To enable the door to close smoothly allow a clearance of 3mm at the top and sides and 6mm at the bottom of the door. Doors come in various sizes so choose a door which is close to the size you require, chances are that you won't find a exact fit so buy a door slightly bigger, this will allow it to be cut to size.

If the door comes with stiles which are used to protect the door in transit, use a try square and draw a pencil line flush with the bottom and top of the door.

Remove the stiles with a hand saw, make sure the saw is kept to the waste side of the pencil line and keep the saw perfectly upright to ensure a square cut is made. Use a plane to to finish off removing the stiles up to the pencil line. Plane from the outside of the door inwards to prevent splintering the edge of the door.

Place the door against the frame and place wedges (chisels will do) underneath to raise the door by approx 6mm to allow for floor covering. Draw pencil lines on the door allowing for a clearance of 3mm at the top and sides, then trim the door up to the lines. If there is a lot of waste use a saw and finish off with a plane, work along the grain on the sides of the door and work from the outside of the door towards the middle at the top and bottom of the door to stop the edge of the door splintering.

When you are happy the door fits with the right amount of clearance place the door within the frame wedging it until it is in the right position, once you are satisfied take a hinge and hold it in position approx 150mm (6") from the top and 225mm (9") from the bottom of the door and mark the top and bottom of the hinge on the door and frame.

Remove the door and support it with the hinge side upwards. Hold a hinge in place so that its knuckle projects just past the face of the door and draw round it with a pencil. Do the same on the door frame again with the knuckle projecting just past the edge of the frame ( not the architrave).

Cut out the recess for the hinge using a sharp chisel. Cut along the vertical lines first and then make a series of cuts across the width of the marked area to the depth of the hinge. Make shallow angle cuts removing the waste until the required depth is achieved. Repeat for all hinges on both the door and the frame.

Place a hinge in the recess on the door and using a bradawl make small pilot holes for the screws then fasten the hinge to the door. Repeat for the other hinge. Place the door up to the frame and use wedges to raise it to the correct height, then fit one screw in each hinge flap, remove the wedges and test the operation of the door. When you are satisfied insert all the screws making sure the heads lay flat otherwise the door will not shut properly.