People might have strange "witch markings" carved into the walls of their house and not even know it.

The public are being asked to look for the unusual symbols in their houses as part of a Halloween effort launched by the government.

The markings have previous been found in historic buildings including the house where Shakespeare was born and the Tower of London. They're thought to have been used as a protection symbol, keeping the people inside the house safe from witches and other threats, and tend to be come from a time when belief in the supernatural was widespread.

'Dia de los Muertos' - Day of the dead festival in Mexico Show all 17 1 /17 'Dia de los Muertos' - Day of the dead festival in Mexico 'Dia de los Muertos' - Day of the dead festival in Mexico Dia de los Muertos is a festival to remember friends and family members who have died and is celebrated throughout Mexico and by people of Mexican heritage living in the United States AP 'Dia de los Muertos' - Day of the dead festival in Mexico A woman holds her baby as she gets helped into her costume in preparation for the start of a Day of the Dead parade along Mexico City's main Reforma Avenue, Saturday, Oct. 29, 2016. Mexico's Day of the Dead celebrations, which traditionally consisted of quiet family gatherings at the graves of their departed loved ones are fast changing under the influence of Hollywood movies, zombie shows, Halloween and even politics. Mexico's capital was holding its first Day of the Dead parade, an idea actually born out of the imagination of a scriptwriter for last year's James Bond movie "Spectre." In the film, whose opening scenes were shot in Mexico City, Bond chases a villain through crowds of revelers in what resembled a parade of people in skeleton outfits and floats. (AP Photo/Dario Lopez-Mills) AP 'Dia de los Muertos' - Day of the dead festival in Mexico Women wearing costumes participate in the "Day of the Dead" parade in Mexico City, Mexico, October 29, 2016. REUTERS/Carlos Jasso Reuters 'Dia de los Muertos' - Day of the dead festival in Mexico A float with a skull figure participates in the "Day of the Dead" parade in Mexico City, Mexico, October 29, 2016. REUTERS/Carlos Jasso Reuters 'Dia de los Muertos' - Day of the dead festival in Mexico Thousands of people try to get a glimpse of a Day of the Dead parade at the main Zocalo plaza in Mexico City, Saturday, Oct. 29, 2016. Hollywood movies, zombie shows, Halloween and even politics are fast changing Mexico's Day of the Dead celebrations, which traditionally consisted of quiet family gatherings at the graves of their departed loved ones bringing them music, drink and conversation. (AP Photo/Dario Lopez-Mills) AP 'Dia de los Muertos' - Day of the dead festival in Mexico A costumed couple poses for a photo during a Day of the Dead parade in Mexico City, Saturday, Oct. 29, 2016. Hollywood movies, zombie shows, Halloween and even politics are fast changing Mexico's Day of the Dead celebrations, which traditionally consisted of quiet family gatherings at the graves of their departed loved ones bringing them music, drink and conversation. (AP Photo/Dario Lopez-Mills) AP 'Dia de los Muertos' - Day of the dead festival in Mexico People look at the "Day of the Dead" parade in Mexico City, Mexico, October 29, 2016. REUTERS/Carlos Jasso Reuters 'Dia de los Muertos' - Day of the dead festival in Mexico A woman dressed in a skeleton costume parades during the annual Dia de los Muertos (Day of the Dead) festival at the Hollywood Forever cemetery in Hollywood, California on October 29, 2016. Dia de los Muertos is a festival to remember friends and family members who have died and is celebrated throughout Mexico and by people of Mexican heritage living in the United States. / AFP PHOTO / Mark RALSTONMARK RALSTON/AFP/Getty Images Getty 'Dia de los Muertos' - Day of the dead festival in Mexico epa05609299 People dressed as a the Death participate in a parade during Day of the Dead celebrations at the Main Square in Mexico City, Mexico, 29 October 2016. EPA/MARIO GUZMAN EPA 'Dia de los Muertos' - Day of the dead festival in Mexico People in costume parade during the annual Dia de los Muertos (Day of the Dead) festival at the Hollywood Forever cemetery in Hollywood, California on October 29, 2016. Dia de los Muertos is a festival to remember friends and family members who have died and is celebrated throughout Mexico and by people of Mexican heritage living in the United States. / AFP PHOTO / Mark RALSTONMARK RALSTON/AFP/Getty Images Getty 'Dia de los Muertos' - Day of the dead festival in Mexico Floats depicting "Catrinas" and other death related characters and offerings march during the first Big Parade of the City to celebrate the Day of the Dead in Mexico City on October 29, 2016. The parade is promoted by Mexico's City Municipality and it is inspired by the James Bond 007 movie "Spectre". / AFP PHOTO / MARIA CALLSMARIA CALLS/AFP/Getty Images Getty 'Dia de los Muertos' - Day of the dead festival in Mexico epa05609300 People dressed and painted as Mexican popular character Catrina and the Death participate in a parade during Day of the Dead celebrations at the Main Square in Mexico City, Mexico, 29 October 2016. EPA/MARIO GUZMAN EPA 'Dia de los Muertos' - Day of the dead festival in Mexico A man in costume takes a selfie during a Day of the Dead parade along Mexico City's main Reforma Avenue, Saturday, Oct. 29, 2016. Hollywood movies, zombie shows, Halloween and even politics are fast changing Mexico's Day of the Dead celebrations, which traditionally consisted of quiet family gatherings at the graves of their departed loved ones bringing them music, drink and conversation. (AP Photo/Dario Lopez-Mills) AP 'Dia de los Muertos' - Day of the dead festival in Mexico epaselect epa05609301 People dressed in traditional costumes participate in a parade during Day of the Dead celebrations at the Main Square in Mexico City, Mexico, 29 October 2016. EPA/MARIO GUZMAN EPA 'Dia de los Muertos' - Day of the dead festival in Mexico People walk in a procession organized by sex workers to remember their deceased colleagues, especially those who were violently murdered, as part of the celebrations ahead of the Day of the Dead, in Mexico City, Mexico October 28, 2016. Picture taken October 28, 2016. REUTERS/Ginnette Riquelme Reuters 'Dia de los Muertos' - Day of the dead festival in Mexico People walk in a procession organized by sex workers to remember their deceased colleagues, especially those who were violently murdered, as part of the celebrations ahead of the Day of the Dead, in Mexico City, Mexico October 28, 2016. Picture taken October 28, 2016. REUTERS/Ginnette Riquelme Reuters 'Dia de los Muertos' - Day of the dead festival in Mexico Famers harvest cempasuchilt and velvet flowers to celebrate the Day of the Dead in Atlixco, Puebla, Mexico. The flowers will be sold at the 'Market of the flower EPA

But a full record of where the symbols appear has never been taken, and so it isn't clear how common they are or where they tend to appear. As such, Historic England has asked the public to look out the for the symbols, and submit any information or pictures that they find so that they can be better understood.

The symbols are known as apotropaic marks and tend to be carved into stone or woodwork near entrances like doorways, windows and fireplaces. IT's thought that they would then ward off witches and evil spirits from entering, keeping the people inside safe.

Markings ranged from a "daisy wheel", the most common type of mark which looks like a flower drawn with a compass, in a single endless line that was supposed to confuse and entrap evil spirits, to "Solomon's knots" and pentangles.

Often they take the form of letters such as AM for Ave Maria, M for Mary or VV, for Virgin of Virgins, scratched into medieval walls, engraved on wooden beams and etched into plaster work to evoke the protective power of the Virgin Mary.

The marks can be found in medieval houses, churches and other buildings, most commonly from around 1550 to 1750.

Known examples include several found at Shakespeare's Birthplace in Stratford-upon-Avon, Warwickshire, where they are carved near the cellar door where precious beer would have been stored, to the Tithe Barn, Bradford-on-Avon, Wiltshire, to protect crops.

Some have been found in caves, such as the Witches' Chimney at Wookey Hole, Somerset, which has numerous markings.

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Duncan Wilson, chief executive of Historic England, said: "Witches' marks are a physical reminder of how our ancestors saw the world. They really fire the imagination and can teach us about previously-held beliefs and common rituals.

"Ritual marks were cut, scratched or carved into our ancestors' homes and churches in the hope of making the world a safer, less hostile place.

"They were such a common part of everyday life that they were unremarkable and because they are easy to overlook, the recorded evidence we hold about where they appear and what form they take is thin.

"We now need the public's help to create a fuller record of them and better understand them."