Until the recent advent of magnetic and electronic locking devices. lock mechanisms had involved only two principal methods: a fixed obstruction (or ‘ward’) which prevents any but the correct key operating the lock and a more effective method involving detainers or levers, which are brought together in pre-selected positions by a key. The latter is the principle of the modern range of mortise deadlocks; when properly fitted they are designed to be stronger than a timber door. This means, in the event of a break-in, the wood itself would fail before the lock. The locking bolt is enclosed inside a steel box to prevent the lock being picked; some have up to three anti-picking devices as well. The bolt itself is often enclosed and reinforced with steel rollers which rotate to prevent a thief cutting through the bolt. Once the bolt is locked, it is secured automatically. When more than one lock is fitted you can obtain a key which will open all the locks but you must ask for this when you order the locks. Some manufacturers offer a registration service which ensures replacement keys are only given to the registered lock owners. You should complete the registration document and return it to the manufacturer. Fitting a mortise lock should offer no problems to the experienced DIY person as long as the manufacturer’s instructions are carefully followed. If in any doubt you should contact a professional London carpenter since a poorly fitted lock will be inefficient and may reduce overall security. There is a wide range of mortise locks available and many reasonably priced devices provide good security. The British Standard is worth looking for when choosing locks because those with this stamp are resistant to drilling and manipulation from outside have a minimum of 1000 key variations and comply with a number of other exacting requirements.
Fitting a mortise lock
Different manufacturers will suggest different methods of fitting; but as a rule the lock is placed along the central rail (slightly lower than halfway down the door) on a panelled door or along the outer stile on a hardboard door.
Position the lock on the inside of the door and draw round it; drill a series of small holes in the area marked and chisel out the mortise. Fit the lock into the mortise so it is flush with the edge of the door; drill out key holes on both sides as recommended by the manufacturer and chisel to key-hole shape. Check you have drilled the key holes correctly and the lock is aligned before fitting the lock and escutcheons. The striking plate is secured to the door frame after you have marked out its correct position in relation to the bolt of the lock. Drill and chisel out a mortise for the striking plate and roughly fit the plate to the frame; any adjustments should be made to the plate and not to the lock position.
Fitting a rim lock
This mortise deadlock is not mortised into the edge of the door, but secured through the door. The deadlocking action varies depending upon construction; most deadlock automatically when the door is closed and some require the key to be turned before they deadlock. The lock is supplied in three parts – a key cylinder, deadlocking portion and striking plate or staple. Again, manufacturers will supply detailed fitting instructions relevant to their particular model: in general terms you will have to drill through the door and some manufacturers will supply a template for this. Insert the key cylinder from the outside of the door and cut the connecting bar to length according to fitting instructions. Fit the deadlock to the inside o[ the door and screw the striking plate into the door frame alter alignment. You can buy a pull which fits beneath the key cylinder flange.
Additional security devices
A mortise lock fitted to an interior or exterior door will often be all that is needed to upgrade your home security; however there are certain weak areas which may need additional devices to deter the intruder. For example, the porch door is your first line of defence and should be fitted with a good two bolt five lever mortise lock.
Two bolt mortise lock
This is similar to the standard mortise lock but has an extra latch bolt with the deadlocking function. The lock is suitable for exterior doors. The two bolt version is fitted in the same manner as the standard mortise lock.
Hook bolt mortise lock
This is widely used to secure timber sliding doors. either flush or single ones, provided there is sufficient space to accommodate the box striking plate h the rim of the door. Installation is similar to the standard mortise lock and the deadlocking function can be triggered either by closing the door or turning the key.
Security mortise bolt
This type can be used to secure exterior or interior doors and French windows. They are usually fitted in pairs (to top and bottom of the door) and a standard key opens all the bo1ts. All that is required for installation is a hole of recommended size drilled into the edge of the door and frame. two shallow rebates cut to accommodate the locking plate and the flange and enable the bolt to be fitted flush into the edge of the door and a hole in the face of the door to take the key. A circular bolt is thrown back by the key, which operates from only one side of the door.
Surface fitting bolts
These are the traditional bolts which are usually fitted at the top and bottom of a door. Ensure you use the correct size bolt – for exterior doors the minimum bolt length should be 200mm and the correct size screw: undersized bolts and screws could be forced.
Hinge bolts
These are particularly important for outward opening doors where the hinges are exposed. The bolts fit inside the frame, close to the hinges. The keep is rebated into the door frame and the bolt is fitted into the door by drilling a hole for it. Hinge bolts will provide solid protection for a door and frame even if the hinge pin is removed.
Door chains
These should be fitted to front and rear exterior doors as a precaution against casual visitors; they allow you to examine visitors’ credentials and prevent violent intrusion into the home. Always keep them fixed when the house is occupied. They are easily fitted with screws. Some types incorporate an unlockable plunger which enables the chain to be secured when leaving the house and also prevents a successful intruder locking you out of the house.
Door viewer
This is essential when outward vision is hampered by solid door construction or frosted glass; fit a porch light as well for night use. The door viewer comes in two parts, one part screwing into the other through the door. Drill a hole of the required size through the door to fit a door viewer; place a block of wood behind the door when drilling to prevent the drill bit bursting through and damaging the finish of the door.
Anti-jemmy plates
These are used where there is a perceptible gap between the edge of the door and the door frame. They are mounted to reduce this gap and to prevent the use of jemmies and other devices of the housebreaker, which might open a non-deadlocking rim lock for example.