The love padlocks, called cadenas d’amour, multiplied until there were thousands of love tokens on the bridge, each engraved with a message of love. (Photo by Charles Platiau/Reuters)

Police haul a youth to the paddy wagon as an undetermined number of arrest were made in downtown Atlanta, Georgia, February 25, 1971, as police moved in to disperse black youths after windows were broken and rocks and fruit thrown in what officers called “a major disturbance”. (Photo by Charles Kelly/AP Photo)

Tami Varma, right, and her brother Robin, the grandchildren of Devendra Varma, a scholar of English gothic tales and an expert in vampire lore, pose in coffins at the Bran Castle, in Bran, Romania, Monday, October 31, 2016. A Canadian brother and sister are passing Halloween night curled up in red velvet coffins in the Transylvanian castle that inspired the Dracula legend, the first time in 70 years anyone has spent the night in the gothic fortress, after they bested 88,000 people who entered a competition hosted by Airbnb to get the chance to dine and sleep at the castle in Romania. A portrait of medieval prince Vlad the Impaler is placed on the wall. (Photo by Vadim Ghirda/AP Photo)

People take part in a Halloween street party at Lan Kwai Fong on October 31, 2016 in Hong Kong. Halloween, a contraction of All Hallows' Evening, falls on the day before All Saints' Day on November 1, a holiday when Christians remember their deceased loved ones. (Photo by Lam Yik Fei/Getty Images)

In this aerial view the officers' building and an auditorium stand at the former Soviet military base on January 26, 2017 in Wuensdorf, Germany. Wuensdorf, once called “The Forbidden City”, was the biggest base for the Soviet armed forces in communist East Germany from 1945 until the last Soviet troops left in the early 1990s following the end of the Cold War and the reunification of Germany. (Photo by Sean Gallup/Getty Images)

A man presents a self-made robot that local media reported is able to carry a person, in Heihe, Heilongjiang province, China, April 5, 2017. (Photo by Reuters/China Daily)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

In this April 2, 2015 photo, dog owner Laura Aquilina strolls with her two year old Rottweiler Brutus, who was recently fitted with prosthetics on all four paws, and is currently learning to use them, near Aquilina's home in Loveland, Colo. Brutus lost all four paws to frostbite as a puppy while under care of a breeder, and Aquilina began caring for him about a year ago. (Photo by Brennan Linsley/AP Photo)