Extra police are being drafted in to Manchester as the city prepares for one of its busiest days of the year.
Metal detecting archways are part of a massive security operation as thousands of people head into the city.
Ch Insp Chris Hill, of Greater Manchester Police, said the number of Christmas drinkers meant the day is known as "Mad Friday".
He said: "Drink responsibly, plan how you are going to get home safely and stick with friends."
He added: "Think about your own actions and stay away from trouble or we will have no problem putting you up in our cells for the night."
The force said it was placing the knife arches in areas where there was a heavy footfall to reassure to the public "that carrying weapons will not be tolerated."
An ANPR (automatic number plate recognition) operation will also be in progress during the weekend.