My Science School

•  Get the lead in

Forget about oil, which can do more harm than good to a stuck lock. The best lubricant for a lock's inner mechanism is graphite, and a good source of graphite is pencil lead. Rub a sharpened, soft lead pencil (B or HB) repeatedly against the matching key, then insert it several times into the lock. Perform this trick twice a year to keep locks in top working condition.

•  Remove a broken key

It happens all the time: keys get old and bent and end up breaking off inside the lock. If you can't enter your house or flat through another door, go to a neighbour to borrow a couple of items before calling a locksmith. First, try removing the broken piece with tweezers. If that won't work, apply a tiny drop of Superglue to the end of the piece that's still on your key chain. Line it up with the part inside the lock, and carefully insert it. Hold it in place for 40-60 seconds and then slowly pull out the key.

•  Light up your lock

To solve the problem of having to come home to a dark verandah, then feeling around for the lock on your front door, dab a few drops of luminous paint around the keyholes of your exterior locks using a cotton bud or small paintbrush. Do the same for any locking bolts on the inside of your house as well, which will make exiting much easier in the event of a power failure, fire or other emergency.

•  Polish a loose doorknob

A wobbly doorknob is often the result of a loose setscrew (a tiny screw found on the doorknob shank), which keeps the knob firmly in place on the spindle. Everyday usage can cause setscrews to become loosened, but you can keep them in place by brushing a little clear nail polish onto each screw after you have tightened them.

•  Pamper a noisy hinge

Is a squeaking door hinge making you feel unhinged? A few drops of baby oil applied around the pin should solve the problem. When you can't find any baby oil and you are out of WD-40, a bit of cooking spray, petroleum jelly or even shaving cream could also be used to silence a squeaky hinge.

•  Re-fix a hinge screw

A loose hinge will cause a door to stick or become difficult to open or close. Tightening the hinge screws usually solves the problem, but if an undamaged screw won't grip, it means the hole has become worn.

To fix it, slide a magazine or two under the opened door to prop it up, if necessary, and then remove the screws from the loose side of the hinge so that it can be folded back. Loosely fill the screw hole with wooden toothpicks or matchsticks that have been dipped in some woodworking adhesive. Keep them flush with the frame by trimming off any protruding ends with a utility knife. When you screw back the hinge, the extra wood should hold the screw firmly in place.

•  Pop goes the rusted bolt

Loosen a rusted bolt by rubbing it with a few tablespoons of a fizzy drink.

•  Unstick a stuck door

If a door sticks because it rubs against the floor or threshold, try this simple fix. Gaffer-tape all four edges of a coarse sheet of sandpaper to the floor where the door rubs, then open and close the door back and forth over the sandpaper until it swings smoothly.

A door that is sticking in its frame (because of too much painting or because it has swollen) can be cured by using an electric plane, hand plane or belt sander to remove the high spots from the door where it is binding. Re-paint after removing the offending wood.

•  Rub out window scratches with toothpaste

Squeeze a small amount of toothpaste onto a soft cotton cloth and vigorously polish the scratch for a minute or two. Wipe off the excess with a damp rag and the scratch should be gone. Be sure to use plain white paste — no gels or striped varieties. You can also use an extra-whitening toothpaste or tooth powder; most have higher amounts of abrasive.

•  Stop cracks in their tracks

You can buy yourself some time before replacing a cracked window by applying a couple of coats of clear nail polish over the crack on both sides of the window. Once dry, the polish should seal any holes in the glass and contain the damage.

•  Stifle a rattle with a matchbook

A rattling sash window is bound to rattle your nerves, especially when you're trying to sleep. Silence the racket with a small folding book of matches. Slide the thin end of the matchbook in between the sash and the loose corner of the window frame. Wedge it in as far as you can, but leave at least a third of the matchbook exposed for easy removal. Then give the window a few light tugs to make sure it won't shake on blustery nights.

•  Plug a draughty window leak

A draughty window is guaranteed to suck out precious heat from your home and raise your fuel bills. What can you do if it's winter and you don't have a sealant gun (or the one you have has dried up)? It's simple. Once you've located the source of the draught (it's often along the top of the lower sash or in a corner between the sash and window frame) take two paper towels, sandwich them together, and fold them up from the bottom 25mm at a time until you have a thick padded strip. Lay the pad over the air leak and secure it on all sides with masking tape.

•  Straighten that sag

Hinged windows can sag when corner joints have weakened. A quick fix is to add flat L-shaped steel corner plates, which cost very little, with matching countersunk screws. From the outside, with the window closed, drive wooden wedges between the window and its frame to close up any loose joints (or to raise a dropped window), and simply screw the plates in place over the corners. Apply metal primer and topcoat to prevent the plate rusting.

•  Removable secondary glazing

If you have single-glazed windows, you can halve the heat lost through them by fixing plastic-sheet double glazing. The plastic sheet can be ordered cut exactly to size and is held in place with a magnetic strip secured to the window and a matching metal strip secured to the frame. The strips need to be cut to length (with sharp scissors or a utility knife) and the backing paper peeled off as they are applied. Unlike film double glazing, sheet glazing can be applied just to the window (so it still opens) and it can be removed in summer when it's no longer needed.