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Padlocks come in four main designs:  Long shackle, open shackle, closed shackle and straight shackle.  They are all available with key or number combination locking.  Long shackle padlocks allow for more flexibility, but they are easier to attack.  Conversely the closed shackle padlocks are more difficult to attack, but are less versatile and are generally used with specific fittings.  Straight shackled padlocks are often used for locking shutters, gates, barriers and chains.  Because most of these padlocks are used outdoors you should make sure that they are resistant to corrosion.

Like everything else in life, ‘what you pay is what you get’.  In 2011, the cheapest ‘Christmas cracker’ type padlock will cost as little as £2, but it won’t be worth using.  A decent secure padlock to security grade 3 (see below) will set you back around £25 and a grade 4 will cost around £60.

I recommend the use of padlocks and padlock fittings that have been successfully type-tested for conformity to all of the requirements of  BS EN 12320: 2012 Building hardware. Padlocks and padlock fittings.  Requirements and test methods.   I particularly recommend the use of padlocks and padlock fittings that are subject to regular audit testing.  I also recommend padlocks that carry the ‘Sold Secure’ mark.  For further information about Sold Secure visit the  Library .

BS EN 12320 classifies padlocks and padlock fittings using a standard 7 digit coding system, which you should find on the packaging or maybe on the padlock or fittings, although the first 5 digits are not used for padlocks.   The coding will look like this:

- - - - - 3 4   

Digit 6 refers to the corrosion resistance of the product where the number 1 means internal applications and the number 3 means external applications.

Digit 7 refers to the security level of the padlock and padlock fittings and the grades range from 1 at the lowest security end to 6 for the highest security. Security ratings of 3 and 4 would be sufficient for most domestic applications, but further advice can be sought from a member of the Master Locksmiths Association.

The tests that are carried out on padlocks and their fittings represent the types of attacks that thieves use.  A grade 2 security padlock will give you a 1000 key differs and will have some resistance against pulling, twisting and cutting of the shackle.  A grade 3 security padlock will have 2500 key differs and its shackle will be about twice as strong as a grade 2 padlock.  A grade 4 security padlock has 5000 key differs and its shackle will be about twice as strong as a grade 3 padlock.  It will also have been tested at a temperature of minus 20° Centigrade.  Security grades 5 and 6 are for much higher security applications and will be used to secure things like shipping containers and warehouse doors.  On websites selling padlocks and sometimes on the packaging you will often see ‘CEN 4’ or ‘CEN Grade 4’.  This number is describing the security grade.

It's equally important that the padlock is used in conjunction with a hasp and staple or padbolt or other fitting that is as secure as the padlock.  Also, the fitting has to be very securely fixed to the door or whatever it is that you are locking.  For example.  If you're locking a shed door, don't just rely on the supplied screws.  You should bolt the fitting through the door and have the nuts on the inside of the door.  In some instances it would be wise to use washers on the inside too, to help prevent the bolts from being pulled through.  Take a look at Security for Garden Outbuildings for some additional advice.

Updated August 2017