Locksmith tools: names, pictures and what each one is used for

What this page is for

Locksmithing is a legitimate trade and most of it is unglamorous: fitting locks, replacing worn cylinders, easing sticking doors, cutting keys and making things secure.

It is worth being clear about scope. This page covers fitting, repairing and maintaining locks on property you own or are engaged to work on. Carrying tools designed to bypass locks without lawful reason is an offence in many places, and the specific rules vary by jurisdiction. If you are locked out of your own home, a locksmith is usually quicker and cheaper than the damage that comes from improvising.

The genuinely useful skill for a homeowner is diagnosis: knowing whether a lock has failed, a door has dropped, or a cylinder simply needs lubricating.

Your own property, or work you are engaged to do

That is the scope here. The legal position on bypass tools varies and possession without lawful reason is an offence in many places.

Diagnose before you buy anything

Most lock complaints are alignment or lubrication, and neither needs a new lock.

Locked out is a job for a locksmith

Faster and cheaper than the damage improvising causes, and they carry the right tools legitimately.

Check the standard before replacing a lock

Insurers frequently specify a standard for external doors. Fitting a lock below it can affect a claim.

Keep a record of what is fitted where

Cylinder sizes, handing and key numbers. It turns a future job from a survey into a five minute swap.

The lock has probably not failed

A door that is hard to lock, a key that needs lifting or a bolt that will not throw is usually reporting on the door rather than the lock. Timber moves with the seasons, hinges wear, and uPVC doors drop on their hinges over the years.

The test is simple: open the door and operate the lock with nothing to engage. If it works smoothly in fresh air, the lock is fine and the problem is alignment. If it is stiff open as well, then look at the lock.

That single check saves more unnecessary lock replacements than anything else, and the fix is often a hinge adjustment or a keep moved by two millimetres.

Operate the lock with the door open

Smooth open and stiff closed means alignment, not the lock. This is the first thing to try, always.

Look for witness marks on the keep

Shiny or scraped metal shows exactly where the bolt is fouling and which way it needs to move.

Check the hinges before the lock

A dropped door is the commonest cause. On uPVC the hinges are adjustable in two or three directions.

Lubricate with the right thing

A dry PTFE or graphite lubricant in a cylinder. Oil and grease attract dust and eventually gum it up completely.

A key that turns hard is a warning

Cylinders give notice before they fail. Sort it before you are standing outside in the rain.

Never force a key

A snapped key in a cylinder turns a small job into a drilling job. Stop and find out why it is stiff.

Fitting a lock, and where it goes wrong

Fitting is measuring and careful cutting. The failures are consistent: the mortice is cut in the wrong place, the cylinder is the wrong length, or the keep does not line up with the bolt.

Cylinder length matters more than people expect. A euro cylinder that projects beyond the handle plate can be gripped and snapped, which is a common method of forced entry. It should sit flush or nearly so, and the two halves are frequently different lengths.

The other detail is that a lock is only as strong as what it goes into. A good lock in a thin frame with short screws is a good lock in a weak door.

Measure the cylinder from the fixing screw

Euro cylinders are measured each side of the centre screw hole, and the two sides are often unequal.

Do not let a cylinder project

A protruding cylinder can be gripped and snapped. Flush or very slightly under, and consider an anti snap type.

Reinforce the frame, not just the door

Most forced entries break the frame. Long screws into the studwork and a decent keep matter as much as the lock.

Mark from a template or the lock itself

Guessing the mortice position leaves an oversized hole you cannot make smaller.

Fit the keep last and to the bolt

Throw the bolt, mark where it actually lands, then cut the keep to that. Never the other way round.

Test it fifty times before you finish

Lock and unlock repeatedly, with the door open and closed. Faults show up on the tenth try rather than the first.

What to buy first, in order

Stage one: diagnosis and adjustment

Screwdrivers including a good set of hex and torx keys, a tape, a marker, a spirit level, PTFE lubricant and a torch. Most call outs need nothing more.

Stage two: fitting and replacing

A cordless drill and driver, a set of auger and flat bits, a hole saw set, wood chisels, a mallet, a mortice chisel and a hand file set.

Stage three: cutting doors and frames

A jigsaw or multi tool, a lock morticer or a router with a jig, a plane, a rasp and a set of long frame fixings.

Stage four: keys and specialist

A key cutting machine and blanks, a pin kit and follower for rekeying, a plug spinner and a cylinder gauge. Safe and access control tools beyond that.

Mistakes that cost a door

Replacing a lock that was never faulty

The commonest error. Test the lock with the door open first, because alignment mimics lock failure exactly.

Letting the cylinder project past the handle

It can be gripped and snapped, which is a known method of forced entry. Measure properly and fit flush.

Short screws into the frame

The lock holds and the frame splits out. Long screws reaching the structure behind the lining.

Cutting the mortice before checking the lock body

An oversized mortice cannot be made smaller, and a packed out lock is never solid again.

Oiling a cylinder

Oil holds dust, which becomes a paste, which eventually stops the pins moving. Dry lubricant only.

Forcing a stiff key

It snaps in the cylinder and a five minute job becomes a drilling and replacement job.

Fitting the keep to the drawing rather than the bolt

Throw the bolt and mark where it lands. Doors are never exactly where the instructions assume.

Ignoring the insurance standard

External door locks frequently have to meet a specified standard, and fitting below it can affect a claim.

Looking after locksmith tools

Keep chisels genuinely sharp

A sharp chisel cuts a clean mortice wall. A blunt one crushes the fibres and the lock never sits square.

Replace worn driver bits

A rounded bit destroys screw heads, and a chewed screw in a lock body is a job you cannot finish.

Look after the key machine cutter and clamps

A worn cutter or a loose clamp gives keys that nearly work, which is worse than keys that obviously do not.

Brush swarf out of everything

Metal filings get into a lock body and into a key machine, and both then work badly for reasons you cannot see.

Store hole saws and bits dry

They live in a van and rust quickly, and a rusty pilot bit wanders off centre.

Label and organise cylinders and spares

The value of a stock of parts is entirely in being able to find the right one quickly.

Frequently asked questions

What locksmith tools do I need to start?

For diagnosis and adjustment, which covers most problems: screwdrivers, hex and torx keys, a tape measure, a marker, a spirit level, a dry PTFE lubricant and a torch. Add a drill, hole saws and chisels for fitting and replacing locks.

Is it legal to own locksmith tools?

Fitting and repair tools, yes. Tools designed for bypassing locks are treated differently, and possession without lawful reason is an offence in many places. The rules vary by jurisdiction, so check locally if you are unsure.

Why is my door suddenly hard to lock?

Usually the door has moved rather than the lock failing. Test it by operating the lock with the door open: if it works smoothly there and sticks when closed, the problem is alignment, and often just a hinge adjustment or a keep moved a couple of millimetres.

How do I measure a euro cylinder?

From the centre of the fixing screw hole to each end, because the two halves are frequently different lengths. Note both measurements, and make sure the cylinder sits flush rather than projecting past the handle plate.

Why should a cylinder not stick out past the handle?

Because a projecting cylinder can be gripped and snapped, which is a known method of forced entry. It should sit flush or very slightly under, and on an external door an anti snap cylinder is worth the difference.

What lubricant should I use on a lock?

A dry PTFE or graphite based lubricant. Oil and grease attract dust, which forms a paste and eventually stops the pins moving altogether, so a lock that was merely stiff becomes a lock that has failed.

What is the difference between a mortice lock and a cylinder lock?

A mortice lock sits in a pocket cut into the edge of the door. A cylinder lock, such as a nightlatch, mounts on the face of the door with the cylinder passing through it. Mortice locks are generally more secure and more work to fit.

Can I fit a lock myself?

A like for like replacement is usually straightforward. Cutting a new mortice is a woodworking job needing sharp chisels and accurate marking, and it is easy to cut oversize. Check the insurance standard for external doors before choosing a lock.

What is rekeying and how is it different from replacing a lock?

Rekeying changes the pins inside an existing cylinder so it works with a different key, keeping the hardware. Replacing swaps the whole cylinder. Rekeying is cheaper across several matching locks and needs a pin kit and a follower.

Why did my key snap in the lock?

Almost always because it was stiff and got forced. Cylinders give warning before they fail, and a key that needs lifting, jiggling or real pressure is telling you something. Stop and find out why rather than pushing harder.

What is a door drop and how do I fix it?

The door sagging on its hinges so the lock no longer aligns with the keep. On uPVC and composite doors the hinges are adjustable in two or three directions with a hex key. On timber doors it may mean packing or repositioning a hinge.

Do I need a key cutting machine?

Only if you cut keys regularly. They are a real investment and they need the cutter and clamps kept in good order, since a worn machine produces keys that almost work, which causes more trouble than keys that clearly do not.