Knocker wrenching was the removal by twisting, breaking or wrenching them out off Georgian, Victorian or Edwardian front doors. This was a night time activity, sometimes reported in outraged newspapers as a craze of students and lordly drunks, certainly in Britain and New England, and possibly elsewhere, from the late 1700s, and one case in Bristol even attracted the attention of the Duke of Wellington.
 
Wrenching knockers differed from stealing knockers in that the perpetrators of the former seem to be middle and upper class men doing it for pleasure, while the latter seem to be working class people thieving for necessity for which the crime was punished by small fines or a reprimand for the former, and in Georgian and early Victorian times with fairly onerous results, including whipping and transportation, for the latter. Later Victorian and Edwardian misdemeanours were punished more evenly and usually by fines.
 
Door knocker thefts seem to have started in the 1700s. For example, Londoners William Keys and Charles Bennet were found guilty of stealing brass knockers from gentlemen's doors in 1722 for which they paid the penalty of being 'whipped at the cart's tail' from Holborn Bars to King Street, a distance of around a mile, with a brass knocker hanging over their heads to denote the crime. The punishment was fairly severe although the public whipping of women was abolished in 1817 and that of men in the early 1830s.
 
By the early 1800s the nobility joined in. Lord Waterford was known as the mad marquis in his younger days during which he stole brass door knockers in London's West End and apparently painted a peeler red in Melton Mowbray.
 
Stealing door knockers must have made a lot of noise, and so it was that the activity became known as 'noisy-dog racket', according to the 1811 Grose Dictionary of the Vulgar Tongue, possibly indicating the necessity of having a barking dog or two around during the theft.
 
Captain John Need of the rifle brigade, stationed in Bristol, and Hon Charles Churchill were brought before the bench in 1848. The accused, one of whom was in 'the garb of a navigator' and the other a gentleman, at 2am were arrested having pulled down railings and a marble door plaque, stealing a doorknocker. Prior to this the locals had complained of bell handles, knockers and door plates being stolen and suspicion was placed on privates of the rifle corps, so the commander of the brigade sent out nightly patrols but this failed to stop the problem. The Duke of Wellington heard about the case and sent one of his top generals to the barracks to sort things out. It just so happens that the Iron Duke, after whom a door knocker was named, was a member of Crockford's club whose 'younger habitués, numerous high-born, high-spirited hooligans would sally forth from Crockford's late at night and embark on an orgy of drunken pranks' … including stealing door knockers. Wellington appears not to have commented further on Captain Need's exploits.
 
In 1874 the Bath Chronicle reported that an important emblem of civilisation and gentility - the door knocker - was again subject to the very reprehensible practice of knocker wrenching in the city, as well as lamp smashing also being freely indulged in. In Dublin in 1901 James Redmond 'who had always been a respectable young man' of Trinity College broke a pane of glass at the College restaurant, stole brass knocker from the Empire Theatre for which the judge fined him £1 or 14 days imprisonment. This failed to stop the outbreak as 'Dublin was badly bitten by the knocker-wrenching craze' in 1904 when 93 knockers were taken off and three students were fined a guinea each. In 1907 another student was defended in court by Mr Ross, a barrister, who raised laughter in court when he said, "We all remember the days of our youth, and the cases of knocker-wrenching and how sometimes knockers were hung up in students quarters as trophies or spoils." The engineering student had to pay a 10s fine or 7 days in gaol. In 1875 Mr. Carter from Forest of Dean who had been staying at the Christopher Hotel in Bath was found to have a number of knockers in his posession, the proceeds of several knocker-wrenching expeditions which had 'greatly exercised the police' at the time.
 
On a Saturday night in Bantry in March 1892 a party went round the town 'wrenching off the knockers of almost every door in town'. Trade signs were also removed from shopfronts and erected on other houses.
 
In 1903 Lord Charles Beresford, one of the 'mad Beresfords', wrenched off an antique silver Venetian knocker from a house in Berkeley Square, London, by tying a rope to it attached to his handsom cab. He succeeded in detaching both the knocker and ripped off part of the front door which he bore away in triumph, settled later when the knocker was returned and damages paid.
 
In 1939 Superintendent Heritage in Horsham said that motorcycle clubs which organised treasure hunts for knockers, "Came into the country feeling they could break into houses and take things." The chairman of the bench called it most disgraceful. Leonard Quick, an aircraft engineer of Tooting and member of 'The Dons', claimed he did not realise taking a door knocker from a house under construction was stealing and was bound over for 12 months and ordered to pay £2 18s 8d costs.
 
In 2002 a Salvo theft alert was raised for a bronze ring door handle (similar to a knocker) in the Romano-Celtic rustic manner stolen from Adel church in north Leeds with a lion mask with a man's head in its mouth dating from c1200s with a 10ins diameter circular tooled backplate and a tooled ring striker (see link below).
 
More recently, in 2011, a heroin addict who managed to steal over 100 knockers, possibly 129 from Gateshead, before being caught was given a community order, continued to thieve and was finally jailed for 18 months. A Sedgley man was given a 12 month community order for stealing brass letter boxes. Chatteris was plagued by metal thieves who stole door knockers and numbers where police officers suspected rising scrap metal prices were the motive behind the thefts.
 
In 2012, in the USA a rash of over a dozen brass door knocker thefts were reported in Society Hill, Philadelphia. Meanwhile Leicester police believed that scrap metal theft was the reason behind theft of door knockers from 21 homes. In 2014 during a spate of knocker thefts in Bolton one couple reported 'relatively low value' modern knockers stolen three times in 18 months.