Here is a step-by-step guide to replacing a piece of damaged drywall by inserting a patch. This a task that can be undertaken by most competent handymen – the hardest part is probably going to be getting the smooth finish over the patch.

You will need the following: a piece of drywall to use as a patch; a straight edge at least 4-inches longer that the section of drywall to be replaced; a keyhole saw; a pencil; a 4-inch putty knife; a sharp utility knife; sandpaper; and some drywall compound (or mud).

1. Using the keyhole saw, cut out the section of damaged drywall. You need to cut out an approximate square, removing all of the damaged area.

2. From the new drywall which is to be used as a patch, cut a square that is about 2-inches larger all the way around than the hole to be filled. So if the sides of the square you have cut out are 6-inches long, the patch will be a square with sides 10-inches long.

It may seem odd to cut a patch that's larger than the hole, but there's a good reason for doing so.

3. Lie the patch face-down on a flat surface. Using the pencil draw onto it lines 2-inches in from each edge, forming what looks like a tic-tac-toe grid. The center square of the grid should be the same size as the hole to be patched.

4. Score the pencil lines on the drywall patch with a sharp knife. Then fold over each side of the square along the scored lines, and break off the gypsum and the rear sheet of paper. You should now be left with a square of drywall which has a sheet of paper on the front that is larger than the hole to be patched.

5. The patch needs to be slightly smaller than the hole in the wall, so that it can easily be inserted, and fits loosely.

6. Put a coat of drywall compound all the way around the hole, and on the edges inside the hole; don't be afraid to apply it generously. Then push the patch into the hole and squeeze out the excess mud.

7. Use the putty knife to smooth out the paper on the front of the patch so that it lies flush on the existing wall. One word of warning – avoid putting too much pressure on the patch itself otherwise you will push it deeper into the wall.

8. Leave the patch to dry out overnight.

9. Sand down any high points, and apply another, very thin, layer of compound over the entire patch. Again, leave it to dry overnight.

10. You can now sand it down and repaint. The hole is now patched.